Post categories unavailable

Hello, the post categories are not accessible and I get a 404. If I call up the categories in the WordPress backend under Posts -> Categories, select one and tap on Preview, I am either forwarded to any post in the category, or the 404 simply appears page.

The category "Haushalt" forwards me to the post "haushaltsschere". For example, the "Garten" category throws a 404.

Here the Links:
https://bestencheck.de/haushalt
https://bestencheck.de/garten

I have not set any redirects.

Here is a picture of the post category page: