[HugoL]

@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.

Some of the string codes are not missing and it still doesn't work. "More like this" (in en_gb) has already been translated from "Similar" en_us to "Änhnlich" in the de_de strings file. I guess More like this and similar mean the same as they both share the same #31622, just BE and AE.

msgctxt "#31622"
msgid "Similar"
msgstr "Ähnlich"

It's still showing "More like this" though. The Kodi language and region has been set to regional > language > german. Am I missing a setting somewhere?
Thanks again

So you're saying it has been localised in the Germany strings.po but still not displaying the translation? Sounds like a strange issue. However, a work-around would be to manually change these labels (if you can find them).  I can't go on a hunt through XMLs right now but the method is to search for the radio button that you want to change the label of. 

So as an example and in your particular case, you're looking for a includesdialogvideoinfo.xml (think that's what it's called, it's been a long time since I worked on these xmls)

ctrl + F to search for all instances of

Code:

<label>$LOCALIZE[31622]</label>

Replace with

Code:

<label>Ähnlich</label>