Can’t assign category to post and new posts will not displayed anymore

Hello everyone,

I have a big problem. Since I installed Polylang, I can no longer assign categories to my pages.

I have a website with a total of 5 languages. On each of these 5 homepages, news of the respective language is displayed. Strangely, these pages do not update any more, but only the German page does, because it is declared as the default language.

If I now open the English news site (in the frontend), for example, I only see old posts. If I open the same news site in the backend, it shows me the current posts. If I mark the post blocks and want to assign a different category to them, only the category “German” (default language) is displayed. All other categories are no longer visible.

However, as soon as I deactivate Polylang, all categories are visible again and can also be assigned. I don’t understand what the problem is.

I also publish my posts regularly via RSS feed on a Telegram channel. Since I installed polylang, only the German channel (default language) is updated, all other channels are dead! The feed adresses are correct.

I’m really starting to despair. I have already deactivated and reactivated all plugins, but it didn’t help. The problem seems to be Polylang, for whatever reason?!?!

I hope someone here can help me.

Thanks in advance
Greetings seto76

The page I need help with: [log in to see the link]