Tremendous packet loss problem

Hello,
I've been playing on aternos servers for about two weeks now, but since yesterday I have so much packet loss whenever I connect to my friends' server (it goes up to 40% and never goes below 10%) that I really can't play at all. I'm the only one experiencing this much lag and that's the only server where it happens to me. What can i do to fix this problem?

Quote from Jervy

Maybe your connection is slow.

If this were the case then i should have this problem in every server, while i only lag on this server.

It seems my router is causing this problem, as using a different one lets me play normally. Does anyone know what to do to fix my router?

Yes, i tried restarting and resetting it to no avail