OK, figured that I had to upload the language pack file. Ok, another thing sorted out, but I am not done yet.
Now when I go to the Extension I am presented with “Deutsch” and “English”. Under each language there are the three default fields (Summary, Body, Extended). I expect the Extension to work as following: I translate the standard field, e.g. “Summary” to “Zusammenfassung”, change the CP’s language to German (My Account -> Personal Settings -> Localization Settings) then go over to the “Edit” tab and the fields labels are presented with the translated word (in this case “Zusammenfassung” instead of “Summary”).
Unfortunately that’s not happening. Or am I getting something terrible wrong?
Info: I am on a brand-new EE installation and I noticed that the checkbox “Default Labels” in the Extension settings stays always checked no matter how often I uncheck it.