I keep lagging on aternos servers exclusively

I keep lagging on aternos servers exclusively. This started happening about a day or two ago, I was playing skyblock with my friend when I started lagging like hell and I could barely join the game, I couldn't even interact with anything. I was just frozen in place in his point of view. We tested it on another server and it lags but less, i can still do basic actions like going outside and punching things but it's very laggy. I host the skyblock server and he hosts the other one. How do I fix this? I have no plugins or mods installed except optifine btw, but it works fine on other servers and it worked fine until a day or two ago.

Quote from Toothy

What does /tps say?

I just turned on the server and tried /tps but its an invalid command

Quote from Toothy

Use Paper, not vanilla

What's Paper? How do I download it?

i ran the command around 10 times as soon as i joined but it only registered 4 times. i couldn't do anything else so i logged out

when i started and joined the server, i could still do basic actions like opening chests, breaking and placing blocks, and punching mobs. it was still very laggy though, lag experienced by players with above 500 ping, but when i pressed tab i had 5 green lines. only when it started getting unplayable and i was teleporting, zombies had insane reach, and i couldn't interact with blocks did i have 3 green lines. I also ran a ping in cmd and these are the results: