So I tried following steps now (according to workarround list from June!):
checked my router firmware - It's up to date
Restarted router - still DCs
changed DNS servers in my network-adapter fromm automatic to google - still DCs
excluded Apex Legends and Easy Anti Cheat from firewall and virusdetection - still DCs
restarted router (unplugged power cable 10 minutes) - still DCs
tried London server - still DCs (like Frankfurt 1+2, Belgium 1-3 and Amsterdam)
tried DNS flush (deletes DNS cache) via command console - still DCs
repaired installation of Apex LEgends - still DCs
Yesterday evening I started Origin and Apex Legend as Admin.
I had a 3 hour session without DCs...
Gonna repport how it works today!