Just how he said.Since you are saying you have 90ms, it must be from other players since when I play I have 12ms and is almost impossible to kill someone with 200+ and on my side, it is very laggy when they move.
I'm not sure they can fix it and all you can do is get used to it ig?
I recommended using an Ethernet cable since that helps a lot.
And possibly you're minecraft lagging?
hope you enjoy your time on Jartex.