Hi,
It is nice that you are understanding the WordPress day by day.
Quote:
Next question I have: How can I change the HEadlines of the category-pages?
Categories:
You can change the category name via `Posts > Categories`.
Category name will display on the theme archive pages. Archive pages show the posts that are tagged or categorized in them.
Their headline will show like,
Category: Category Name
Tag: Tag Name
Posts:
Similarly, you can edit or create new posts via `Posts`
Pages:
And pages via `Pages`
Following article will also be helpful to you.
https://codex.wordpress.org/First_Steps_With_WordPress
Thanks