Hey Nikolaus,
The only “general.php” files in The Events Calendar and our other add-ons are in the /template-tags folders of each plugin.
This file and anything else that is not in the /views folder cannot be recreated in your child theme.
Your next question is this:
And can I like in .css files keep only the parts of .php-files in the child-theme-folder that I edited.
I’m not 100% certain what you mean here, but in general you cannot and should mix PHP code into CSS files, or CSS code into PHP files unless you know exactly what you’re doing.
I hope this information helps!
— George