Hi Moritz, Juris, etc,
You are running a fast Tor relay, which is great: http://rougmnvswfsmd4dq.onion/rs.html#details/E0B8AC84A4CD385333BA9BDB28F69F...
But that Tor version is obsolete, and because of old bugs, we will soon cut relays running those versions out of the network. Please consider upgrading!
The Tor 0.3.5 long-term-stable branch will be maintained until Feb 2022: https://trac.torproject.org/projects/tor/wiki/org/teams/NetworkTeam/CoreTorR... and you can see the lifetimes of other Tor versions on that table too.
You can find Tor packages for your distro / OS here: https://trac.torproject.org/projects/tor/wiki/TorRelayGuide#Platformspecific...
Let us know if we can do anything to make the process easier.
And lastly, I am cc'ing the new network health mailing list (which has public archives), to help us stay synced: https://trac.torproject.org/projects/tor/wiki/org/teams/NetworkHealthTeam
Thanks! --Roger