How to insert translations? No language file?

I have not tried "Contest" in SQ and therefore, I still have no imagination of the character of those quizzes. But if they are like you describe it here, then I would agree, that "Wettbewerb" is the German word, that fits better.

I have checked my website before I wrote about the missing German inspite there is a a geramn language file present. The general language is set to German. But as I mentioned, this website is old Joomla 3 and will be replaced by completely new Joomla 4 in fall 2022. I won't invest too much time in it any more. Therefor your hint, to rename the German files to the English file name is a good solution.

I AM VERY SORRY…
When I tried to rename my language files and then saw the result in the backend, I realize, that I must have made a big mistake, because I have only translated a part of the English *.ini file. And by this, most of the backend is not translated and even worse, the items are missing completely.
As far as I can see, the file for the mod is completely translated.