Repeated Error 502 and at some point nothing works anymore

I have set up a fresh GitLab on a Strato vServer and migrated our existing system.
The new server has more performance, but I always get a 500 error.

The log brings the following error message. What can I do?

root:~# tail -f /var/log/gitlab/gitlab-rails/production.log | grep error

lib/gitlab/git/wraps_gitaly_errors.rb:15:in `rescue in wrapped_gitaly_errors'
lib/gitlab/git/wraps_gitaly_errors.rb:6:in `wrapped_gitaly_errors'
lib/gitlab/middleware/handle_ip_spoof_attack_error.rb:25:in `call'

No one has an idea? :worried: