If you don't know the version number, how did you install it?
When did you install b2evolution? How old is the site?

What have you done recently that may have changed something?

in April 2018 I made an update to a newer version. Taht made it crush.

April 2018? That's a long time ago.
Have you been able to log in at all since April? I see the last post is dated 12/04/2018

Howe did you try and upgrade Automatic, which means it may well have been the new version that was around then. Version 6.9.7 came out in February 2018 and6.6.10.1 in May 2018.

If you upgraded by ftp you will have the files so you can check the date and version etc.
Make sure you have a copy of the database and try again with a newer version, say 6.10.5

Looking at your site it seems you have an ajax problem in loading forms

However now I've browsed your site I find this. Part of you site is in odd folders so it looks like a bad install/upgrade.

Save the database
delete all the files if you can and reinstall afresh
If you don't have ftp access to delete the old version completely then install in a new directory, or delete the sub-domain and start again etc.

Look at the second image, and url, you have part of the blog in the install folder