Sorry to hear this, @Christoph!
1. When you say, “But ist is not working,” can you please clarify how the updates are not working? What is happening? Are there error messages? If so, copy and paste the full error messages here.
2. Can you post your site’s complete, un-edited System Information here? You have posted the WordPress version and your theme name, but if possible can you please post the full, un-edited and un-modified System Information for your site to this thread? Here is how to do that ? https://theeventscalendar.com/knowledgebase/sharing-sys-info/
Thanks!
George