Thanks for your answer and the link to the plugin. I installed the plugin but unfortunately it doesn’t work with this theme:
“Dies ist ein Problem in der Programmierung der Quelldateien, die Sie zu übersetzen versuchen. Kontaktieren Sie den Autor und erklären Sie das Problem.”
What this means is that there is an error in the sourcefiles. And that I would need to contact the author of the theme.
In any case what I did now is that I translated and created the german files .po and .mo by myself.
I placed them in the theme folder “lang”.
On wordpress if I go to settings -> general / I am now able to switch the language to german. But all the themes text stays in English
Do I need to rewrite anything in a .php file?
For the future and other users it would be truly nice if this theme could get translated by code styling-localization. If you like I also can provide you the translations that I did.
Looking forward to your kind help!