Thank you for getting back @kinderprogrammieren!
You’re right. CSS code only hides the post meta from screen, but not from the code.
Currently there is no instant setting to remove that code from WordPress dashboard. So you’re required to edit the theme’s file, that is actually not recommended. Because all modified files will be replaced upon theme update in the future. Thus you’ll redo the changes.
That HTML markup for post meta presents in these theme’s files:
inc/template-tags.php
widget/widget-featured-posts-a.php
widget/widget-featured-posts-home.php
widget/widget-most-popular-home.php
widget/widget-most-popular.php
widget/widget-multiple-cats-posts.php
widget/widget-posts-carousel.php
widget/widget-single-category-posts-a.php
widget/widget-video-posts.php
Regards,
Kharis