In the plugin “User Submitted Post” you can easily change the language with the Loco Translate Plugin, but the text “Select Some Options” has to be changes manually. Here is how:
1) Go to the directory User-submitted-posts, choose Resources.
2) Download the file jquery.chosen.js
3) Open it with Notepad and search for “Select Some Options” and change the text. Then upload again.
Sometimes you can’t see the change. Maybe you need to clear cache etc.