[SoulReaver]

Don't really want to look through almost every file in there. Thanks again!

Install Notepad++ and Edit -> Find in files..

@SoulReaver It's not in the german strings.po file, unfortunately. If it would be inside the the file it would translate it, right? Is there a language setting for the skin? I couldn't find any yet but there are so many settings.
Found the label "choose art, more like this" in resource.language.en_gb\strings.po but adding a translation there or adding it to the german strings.po didn't do anything, unfortunately.

You can just copy the missing strings code from the en_gb strings file to the language file of your choice and type the translation in the msgstr line and it will translate to that if your Kodi language is set to that same language in Kodi > Settings > Interface > Regional > Language.