Hi Gabriele.
Please never run EGroupware without SSL! Even in an internal network, malicious software can read your login data.
And some additional software requires SSL.
Please check if there are any package updates pending on your system.
In particular, the version of EGroupware should be 20.1:
You seem to have several problems.
Maybe it would make sense for you to contact our support. We also offer this to CE users:
This will probably help you reach your goal more quickly.
Stefan