diff --git a/app/controllers/submissions_controller.rb b/app/controllers/submissions_controller.rb
--- a/app/controllers/submissions_controller.rb
+++ b/app/controllers/submissions_controller.rb
@@ -16,8 +16,8 @@
     else
       @problem = Problem.find_by_id(params[:problem_id])
       if (@problem == nil) or (not @problem.available)
-        redirect_to main_list_path
-        flash[:notice] = 'Error: submissions for that problem are not viewable.'
+        redirect_to list_main_path
+        flash[:error] = 'Authorization error: You have no right to view submissions for this problem'
         return
       end
       @submissions = Submission.find_all_by_user_problem(@user.id, @problem.id).order(id: :desc)
diff --git a/app/controllers/tasks_controller.rb b/app/controllers/tasks_controller.rb
--- a/app/controllers/tasks_controller.rb
+++ b/app/controllers/tasks_controller.rb
@@ -27,8 +27,9 @@
   def download
     problem = Problem.find(params[:id])
     unless @current_user.can_view_problem? problem
-      flash[:notice] = 'You are not authorized to access this file'
-      redirect_to :action => 'index' and return
+      flash[:error] = 'You are not authorized to access this file'
+      redirect_to list_main_path
+      return
     end
 
     base_name = params[:file]
@@ -37,7 +38,8 @@
 
     if !FileTest.exists?(filename)
       flash[:notice] = 'File does not exists'
-      redirect_to :action => 'index' and return
+      redirect_to list_main_path
+      return
     end
 
     send_file_to_user(filename, base_filename)
diff --git a/app/models/submission.rb b/app/models/submission.rb
--- a/app/models/submission.rb
+++ b/app/models/submission.rb
@@ -154,7 +154,7 @@
       return if self.user.admin?
 
       #check if user has the right to submit the problem
-      errors.add('problem',"must be valid.") if (!self.user.available_problems.include?(self.problem)) and (self.new_record?)
+      errors[:base] << "Authorization error: you have no right to submit to this problem" if (!self.user.available_problems.include?(self.problem)) and (self.new_record?)
     end
   end
 
diff --git a/app/views/main/help.html.haml b/app/views/main/help.html.haml
--- a/app/views/main/help.html.haml
+++ b/app/views/main/help.html.haml
@@ -43,5 +43,5 @@
           %tt <tt>{<br/>LANG: Pascal<br/>TASK: mobiles<br/>}</tt>
     
     %p
-      = raw(t('help.ask_questions_at_messages',:message_link_name => (t 'menu.messages'),:url => url_for(:controller => 'messages', :action => 'list')))
+      = raw(t('help.ask_questions_at_messages',:message_link_name => (t 'menu.messages'),url: messages_path ))
 
diff --git a/db/schema.rb b/db/schema.rb
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -12,69 +12,69 @@
 
 ActiveRecord::Schema.define(version: 2020_08_13_083020) do
 
-  create_table "announcements", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "announcements", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
     t.string "author"
-    t.text "body", limit: 16777215
+    t.text "body"
     t.boolean "published"
-    t.datetime "created_at", null: false
-    t.datetime "updated_at", null: false
+    t.datetime "created_at"
+    t.datetime "updated_at"
     t.boolean "frontpage", default: false
     t.boolean "contest_only", default: false
     t.string "title"
     t.string "notes"
   end
 
-  create_table "contests", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "contests", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
     t.string "title"
     t.boolean "enabled"
-    t.datetime "created_at", null: false
-    t.datetime "updated_at", null: false
+    t.datetime "created_at"
+    t.datetime "updated_at"
     t.string "name"
   end
 
-  create_table "contests_problems", id: false, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "contests_problems", id: false, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
     t.integer "contest_id"
     t.integer "problem_id"
   end
 
-  create_table "contests_users", id: false, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "contests_users", id: false, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
     t.integer "contest_id"
     t.integer "user_id"
   end
 
-  create_table "countries", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "countries", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
     t.string "name"
-    t.datetime "created_at", null: false
-    t.datetime "updated_at", null: false
+    t.datetime "created_at"
+    t.datetime "updated_at"
   end
 
-  create_table "descriptions", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
-    t.text "body", limit: 16777215
+  create_table "descriptions", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
+    t.text "body"
     t.boolean "markdowned"
-    t.datetime "created_at", null: false
-    t.datetime "updated_at", null: false
+    t.datetime "created_at"
+    t.datetime "updated_at"
   end
 
-  create_table "grader_configurations", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "grader_configurations", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
     t.string "key"
     t.string "value_type"
     t.string "value"
-    t.datetime "created_at", null: false
-    t.datetime "updated_at", null: false
-    t.text "description", limit: 16777215
+    t.datetime "created_at"
+    t.datetime "updated_at"
+    t.text "description"
   end
 
-  create_table "grader_processes", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "grader_processes", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
     t.string "host"
     t.integer "pid"
     t.string "mode"
     t.boolean "active"
-    t.datetime "created_at", null: false
-    t.datetime "updated_at", null: false
+    t.datetime "created_at"
+    t.datetime "updated_at"
     t.integer "task_id"
     t.string "task_type"
     t.boolean "terminated"
-    t.index ["host", "pid"], name: "index_grader_processes_on_ip_and_pid"
+    t.index ["host", "pid"], name: "index_grader_processes_on_host_and_pid"
   end
 
   create_table "groups", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
@@ -89,7 +89,7 @@
     t.index ["group_id", "problem_id"], name: "index_groups_problems_on_group_id_and_problem_id"
   end
 
-  create_table "groups_users", options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
+  create_table "groups_users", id: false, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
     t.integer "group_id", null: false
     t.integer "user_id", null: false
     t.index ["user_id", "group_id"], name: "index_groups_users_on_user_id_and_group_id"
@@ -98,13 +98,13 @@
   create_table "heart_beats", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
     t.integer "user_id"
     t.string "ip_address"
-    t.datetime "created_at", null: false
-    t.datetime "updated_at", null: false
+    t.datetime "created_at"
+    t.datetime "updated_at"
     t.string "status"
     t.index ["updated_at"], name: "index_heart_beats_on_updated_at"
   end
 
-  create_table "languages", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "languages", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
     t.string "name", limit: 10
     t.string "pretty_name"
     t.string "ext", limit: 10
@@ -114,23 +114,22 @@
   create_table "logins", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
     t.integer "user_id"
     t.string "ip_address"
-    t.datetime "created_at", null: false
-    t.datetime "updated_at", null: false
-    t.index ["user_id"], name: "index_logins_on_user_id"
+    t.datetime "created_at"
+    t.datetime "updated_at"
   end
 
-  create_table "messages", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "messages", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
     t.integer "sender_id"
     t.integer "receiver_id"
     t.integer "replying_message_id"
-    t.text "body", limit: 16777215
+    t.text "body"
     t.boolean "replied"
-    t.datetime "created_at", null: false
-    t.datetime "updated_at", null: false
+    t.datetime "created_at"
+    t.datetime "updated_at"
   end
 
-  create_table "problems", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
-    t.string "name", limit: 100
+  create_table "problems", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
+    t.string "name", limit: 30
     t.string "full_name"
     t.integer "full_score"
     t.date "date_added"
@@ -151,42 +150,42 @@
     t.index ["tag_id"], name: "index_problems_tags_on_tag_id"
   end
 
-  create_table "rights", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "rights", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
     t.string "name"
     t.string "controller"
     t.string "action"
   end
 
-  create_table "rights_roles", id: false, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "rights_roles", id: false, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
     t.integer "right_id"
     t.integer "role_id"
     t.index ["role_id"], name: "index_rights_roles_on_role_id"
   end
 
-  create_table "roles", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "roles", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
     t.string "name"
   end
 
-  create_table "roles_users", id: false, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "roles_users", id: false, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
     t.integer "role_id"
     t.integer "user_id"
     t.index ["user_id"], name: "index_roles_users_on_user_id"
   end
 
-  create_table "sessions", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "sessions", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
     t.string "session_id"
-    t.text "data", limit: 16777215
+    t.text "data"
     t.datetime "updated_at"
     t.index ["session_id"], name: "index_sessions_on_session_id"
     t.index ["updated_at"], name: "index_sessions_on_updated_at"
   end
 
-  create_table "sites", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "sites", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
     t.string "name"
     t.boolean "started"
     t.datetime "start_time"
-    t.datetime "created_at", null: false
-    t.datetime "updated_at", null: false
+    t.datetime "created_at"
+    t.datetime "updated_at"
     t.integer "country_id"
     t.string "password"
   end
@@ -194,11 +193,11 @@
   create_table "submission_view_logs", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
     t.integer "user_id"
     t.integer "submission_id"
-    t.datetime "created_at", null: false
-    t.datetime "updated_at", null: false
+    t.datetime "created_at"
+    t.datetime "updated_at"
   end
 
-  create_table "submissions", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "submissions", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
     t.integer "user_id"
     t.integer "problem_id"
     t.integer "language_id"
@@ -206,17 +205,16 @@
     t.binary "binary"
     t.datetime "submitted_at"
     t.datetime "compiled_at"
-    t.text "compiler_message", limit: 16777215
+    t.text "compiler_message"
     t.datetime "graded_at"
     t.integer "points"
-    t.text "grader_comment", limit: 16777215
+    t.text "grader_comment"
     t.integer "number"
     t.string "source_filename"
     t.float "max_runtime"
     t.integer "peak_memory"
     t.integer "effective_code_length"
     t.string "ip_address"
-    t.index ["submitted_at"], name: "index_submissions_on_submitted_at"
     t.index ["user_id", "problem_id", "number"], name: "index_submissions_on_user_id_and_problem_id_and_number", unique: true
     t.index ["user_id", "problem_id"], name: "index_submissions_on_user_id_and_problem_id"
   end
@@ -229,7 +227,7 @@
     t.datetime "updated_at", null: false
   end
 
-  create_table "tasks", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "tasks", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
     t.integer "submission_id"
     t.datetime "created_at"
     t.integer "status"
@@ -237,15 +235,15 @@
     t.index ["submission_id"], name: "index_tasks_on_submission_id"
   end
 
-  create_table "test_pairs", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "test_pairs", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
     t.integer "problem_id"
-    t.text "input", limit: 4294967295
-    t.text "solution", limit: 4294967295
-    t.datetime "created_at", null: false
-    t.datetime "updated_at", null: false
+    t.text "input", limit: 16777215
+    t.text "solution", limit: 16777215
+    t.datetime "created_at"
+    t.datetime "updated_at"
   end
 
-  create_table "test_requests", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "test_requests", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
     t.integer "user_id"
     t.integer "problem_id"
     t.integer "submission_id"
@@ -253,13 +251,13 @@
     t.string "output_file_name"
     t.string "running_stat"
     t.integer "status"
-    t.datetime "updated_at", null: false
+    t.datetime "updated_at"
     t.datetime "submitted_at"
     t.datetime "compiled_at"
-    t.text "compiler_message", limit: 16777215
+    t.text "compiler_message"
     t.datetime "graded_at"
     t.string "grader_comment"
-    t.datetime "created_at", null: false
+    t.datetime "created_at"
     t.float "running_time"
     t.string "exit_status"
     t.integer "memory_usage"
@@ -273,20 +271,20 @@
     t.integer "score"
     t.text "input", limit: 4294967295
     t.text "sol", limit: 4294967295
-    t.datetime "created_at", null: false
-    t.datetime "updated_at", null: false
+    t.datetime "created_at"
+    t.datetime "updated_at"
     t.index ["problem_id"], name: "index_testcases_on_problem_id"
   end
 
-  create_table "user_contest_stats", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "user_contest_stats", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
     t.integer "user_id"
     t.datetime "started_at"
-    t.datetime "created_at", null: false
-    t.datetime "updated_at", null: false
+    t.datetime "created_at"
+    t.datetime "updated_at"
     t.boolean "forced_logout"
   end
 
-  create_table "users", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=utf8", force: :cascade do |t|
+  create_table "users", id: :integer, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1", force: :cascade do |t|
     t.string "login", limit: 50
     t.string "full_name"
     t.string "hashed_password"