German translation not working (just a view words)

I don’t know what i should do to get the translations working, i’ve tried everything:
I edited the themes languages files: doesn’t work.
So then i downloaded the stable german translation from tribe-events github and put them into /wp-content/languages/plugins/ : doesn’t work. I put them into /wp-content/plugins/the-events-calendar/lang : doesn’t work.
So i edited the strings in the plugins templates directly – doesn’t work either.
Then i was looking in the other support threads and saw some additional translation in the functions.php. I copied the code and modified the translations but that doesn’t work either. I’m really stuck now since nothing seems to work.

You can find an example here: https://moosrank.ch/spezialwoche/
It should say “Vorherige Veranstaltungen” instead of “Previous Veranstaltungen” and “N?chste Veranstaltungen” instead of “Next Veranstaltungen” and “Weitere Infos” instead of “Find out more”. I found the strings in the .po files but the website won’t take the translations and i really don’t have any idea why. (It’s not the first time where i have to translate strings from the event tribe plugin and i never had that much problems).

Thank you for your feedback.