so, first of all, seeing your comments about this situation and more, I would do one of these things to fix the problem:
1. install newest updates, drivers.
2. make sure pc is optimized.
3. factory reset.
4. cleaning pc.
5. make sure everything is fine with the bios.
6. scan for malware.
7. verify game files.
8. download UserBenchmark and check your pc parts.
if any of the things mentioned above didn't help, then you have a great news kinda, it's the cs itself. many users in the past days are complaining about fps issues after the new update, but idk, for me everything is working great.