I Play on a mod pack server and after the server crashed all effects where gone i tried re-connecting and killing my self but it still doesn't work i still have all advancements
thats why i wanted to ask if someone knows a way to fix that problem

Might be a mod conflict. I suggest talking to the server owner and see if they can diagnose the problem in this way:

1. Remove half the mods, if the bug persists in the remaining half, it's one of those mods.
2. Repeat until only a few mods remain.
3. Remove one at a time until the only mod remaining is the one that causes the problem.

Or ask them to install VanillaFix, as it should give them an idea of what caused the crash.