Hey,
Sorry for writing in English, I've used the translate page to read the whole thread.
I have the same exact issue, I ordered 4 VPS servers today and all of them didnt have internet connectivity.
It does look like some router misconfiguration, because I had multiple previous VPS servers with netcup (debian 12) all working out of the box, SSH-ed straight into them.
I wrote them a support ticket but since its outside working hours I dont expect them to respond today.
All 4 of the servers are in the 152.53.x.x range.
Just wanted to share this and agree with @tiekoetter.
----
PS after edit
I also tried pinging multiple servers from the VNC console provided via the Server Control Panel and I didnt manage to connect/ping to anything.