I'm sorry I need to post thread about this because I know a lot people has this issue but since server is unplayable I'll try to get some help.
I have installed these mods:
Normally I started Aternos server by default (Vanilla 14.4.4) and yesterday I turned it into Forge.
(With vanilla 14.4.4 full without ANY mod, okay.. I had installed Optifine but without Forge, I had lags too)
And I have one datapack and it's: Timber
LOG:
Anyone who could help me I will be so so so happy!
EDIT: I forget to mention It's survival server for max. 4 people but so far only I play on it, so 1 player.