diff --git a/Gemfile b/Gemfile
index 056ce5d7..02789f5b 100644
--- a/Gemfile
+++ b/Gemfile
@@ -37,7 +37,7 @@ gem 'rest-client'
 gem 'rubyzip'
 gem 'mnemosyne-ruby'
 gem 'faraday'
-gem 'proforma', git: 'git://github.com/openHPI/proforma.git' # use version not master
+gem 'proforma', path: '../proforma' #, git: 'git://github.com/openHPI/proforma.git' # use version not master
 gem 'whenever', require: false
 gem 'rails-timeago'
 
diff --git a/Gemfile.lock b/Gemfile.lock
index 4f353f77..862b636c 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,13 +1,3 @@
-GIT
-  remote: git://github.com/openHPI/proforma.git
-  revision: 54a5bdf2bafebb548998c945ee68d099d85108df
-  specs:
-    proforma (0.1.0)
-      activemodel (~> 5.2.3)
-      activesupport (~> 5.2.3)
-      nokogiri (~> 1.10.2)
-      rubyzip (>= 1.2.2, < 2.1.0)
-
 GIT
   remote: https://github.com/gosukiwi/tubesock
   revision: 86a5ca4f7d3c3a7b9a727ad91df3b9b4912eda39
@@ -17,6 +7,15 @@ GIT
       rack (>= 1.5.0)
       websocket (>= 1.1.0)
 
+PATH
+  remote: ../proforma
+  specs:
+    proforma (0.1.0)
+      activemodel (~> 5.2.3)
+      activesupport (~> 5.2.3)
+      nokogiri (~> 1.10.2)
+      rubyzip (>= 1.2.2, < 2.1.0)
+
 GEM
   remote: https://rubygems.org/
   specs:
diff --git a/app/controllers/exercises_controller.rb b/app/controllers/exercises_controller.rb
index d2a90f98..77f35ba4 100644
--- a/app/controllers/exercises_controller.rb
+++ b/app/controllers/exercises_controller.rb
@@ -107,26 +107,7 @@ class ExercisesController < ApplicationController
   end
 
   def export_external_check
-    @codeharbor_link = current_user.codeharbor_link
-    conn = Faraday.new(url: @codeharbor_link.check_uuid_url) do |faraday|
-      faraday.options[:open_timeout] = 5
-      faraday.options[:timeout] = 5
-
-      faraday.adapter Faraday.default_adapter
-    end
-
-    codeharbor_check = begin
-                         response = conn.post do |req|
-                           req.headers['Content-Type'] = 'application/json'
-                           req.headers['Authorization'] = 'Bearer ' + @codeharbor_link.api_key
-                           req.body = {uuid: @exercise.uuid}.to_json
-                         end
-                         response_hash = JSON.parse(response.body, symbolize_names: true)
-
-                         {error: false}.merge(response_hash.slice(:message, :exercise_found, :update_right))
-                       rescue Faraday::Error => e
-                         {error: true, message: t('exercises.export_codeharbor.error', message: e.message)}
-                       end
+    codeharbor_check = ExerciseService::CheckExternal.call(uuid: @exercise.uuid, codeharbor_link: current_user.codeharbor_link)
 
     render json: {
       message: codeharbor_check[:message],
@@ -196,8 +177,12 @@ class ExercisesController < ApplicationController
       exercise.save!
       return render json: {}, status: 201
     end
-    logger.info(exercise.errors.full_messages)
-    render json: {}, status: 400
+    # logger.info(exercise.errors.full_messages)
+    # render json: {}, status: 400
+  rescue Proforma::ProformaError
+    render json: t('exercises.export_codeharbor.export_errors.invalid'), status: 400
+  rescue StandardError
+    render json: t('exercises.export_codeharbor.export_errors.internal_error'), status: 500
   end
 
   def user_from_api_key
diff --git a/app/services/exercise_service/check_external.rb b/app/services/exercise_service/check_external.rb
new file mode 100644
index 00000000..1cce7614
--- /dev/null
+++ b/app/services/exercise_service/check_external.rb
@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+module ExerciseService
+  class CheckExternal < ServiceBase
+    def initialize(uuid:, codeharbor_link:)
+      @uuid = uuid
+      @codeharbor_link = codeharbor_link
+    end
+
+    def execute
+      response = connection.post do |req|
+        req.headers['Content-Type'] = 'application/json'
+        req.headers['Authorization'] = 'Bearer ' + @codeharbor_link.api_key
+        req.body = {uuid: @uuid}.to_json
+      end
+      response_hash = JSON.parse(response.body, symbolize_names: true)
+
+      {error: false}.merge(response_hash.slice(:message, :exercise_found, :update_right))
+    rescue Faraday::Error => e
+      {error: true, message: t('exercises.export_exercise.error', message: e.message)}
+    end
+
+    private
+
+    def connection
+      Faraday.new(url: @codeharbor_link.check_uuid_url) do |faraday|
+        faraday.options[:open_timeout] = 5
+        faraday.options[:timeout] = 5
+
+        faraday.adapter Faraday.default_adapter
+      end
+    end
+  end
+end
diff --git a/app/services/exercise_service/push_external.rb b/app/services/exercise_service/push_external.rb
index b0d8723f..93dacb81 100644
--- a/app/services/exercise_service/push_external.rb
+++ b/app/services/exercise_service/push_external.rb
@@ -10,11 +10,7 @@ module ExerciseService
     def execute
       body = @zip.string
       begin
-        conn = Faraday.new(url: @codeharbor_link.push_url) do |faraday|
-          faraday.adapter Faraday.default_adapter
-        end
-
-        response = conn.post do |request|
+        response = connection.post do |request|
           request.headers['Content-Type'] = 'application/zip'
           request.headers['Content-Length'] = body.length.to_s
           request.headers['Authorization'] = 'Bearer ' + @codeharbor_link.api_key
@@ -26,5 +22,13 @@ module ExerciseService
         return e.message
       end
     end
+
+    private
+
+    def connection
+      Faraday.new(url: @codeharbor_link.push_url) do |faraday|
+        faraday.adapter Faraday.default_adapter
+      end
+    end
   end
 end
diff --git a/config/locales/en.yml b/config/locales/en.yml
index b0a7ccd3..138fa28c 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -337,6 +337,9 @@ en:
         create_new: Create new
         close: Close
         abort: Abort
+      export_errors:
+        invalid: Invalid exercise
+        internal_error: An internal error occurred on Codeharbor while importing the exercise.
     file_form:
       hints:
         feedback_message: This message is used as a hint for failing tests.