So I have a floyd rose from China and it doesn't really stay in tune. the nut for sure isnt the problem. The trem wont stay in tune. When I dive bomb it goes flat and when I pull it back to raise the pitch it goes back in tune. I tried to work the springs and it would still be a half step off on certain strings. I feel like it is impossible to get it function correctly.

So I am thinking of replacing parts of it. Should I replace the saddle or the fine tunes or something?

Let me know what you think. Thanks in advance
If it's going back in tune when you pull it up it's sticking on something. Try taking the back plate off the guitar that covers the springs. I've had a couple of cheaper axes in the past and that's usually the problem.
If you're talking about the trem block being too big for the cavity I am not sure if it is the case.. white working my springs without the back plate the same thing happens.

I really feel like it is impossible to use this trem, but then again trems are made to function correctly and stay in tune right?

like even if I have a low quality one, maybe I just need a higher quality part to make it function right? idk haha
Yeah, if it fits properly, that would probably sort you out.
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It could be the mounting studs. Check to make sure they are tightly secured in the thread inserts. Even with OFR bridges I have encountered this problem sometimes. Even if they seem tight, take some plumbers tape and wrap it around the threads of the mounting stud 1 or 2 times. This will make it sit firmly in the thread insert. If the thread inserts are loose in the body then it is a routing issue and would need to be repaired accordingly.
Also make sure the the knife edges are not dull or chipped, this can cause all sorts of tuning instability.
Another recommendation is to take some chap stick and put it on the studs and knife edges.
If all else fails burn it lol.