working!

app/controllers/admin/translation_controller.rb

 class Admin::TranslationController < Admin::ApplicationController
   def translate
     @target = translation_params[:target]
-    # @response = LibreTranslate.translate  translation_params[:text],
-    #                                       source: translation_params[:from],
-    #                                       target: translation_params[:to]
-    @response = {
-      'translatedText' => 'test'
-    }
+    @response = LibreTranslate.translate  translation_params[:text],
+                                          source: translation_params[:from],
+                                          target: translation_params[:to]
   end
 
   protected