game is acting weird on new PC

Basicly i've not been playing for a long while (approx 5 years) and i've completely upgraded my pc since then, but coming back to the game i feel like everything's kinda glitchy. (my explaining might be a lil bad)

ISSUES:

- i can't switch to shotgun and then sword at the same time i have to delay the keys or it just wont do anything like my pc wouldn't let me press both keys at the same time. (Holding massive and switching is just impossible now)
- when i shoot the shotgun reload and switch to the other one its the same thing, if i dont delay the shooting and reloading it'll just shoot.
- walking in the stairs feels like somebody dropped a whole jar of lube on them, my character just wants to slide
- can barely dbf as i gotta delay the slash and the block as well and so on...

while i do understand that going away 5 years will definetly make a difference on my abilitys and skills, i can remember vividly the way the game behaved before as i spent countless hours as you all did playing this.
(i tried lowering graphic settings and stuff like that but no improvements)

SOME SPECS:

WIN10
CPU Amd Ryzen 5 5600
Motherboard MSI B550M PRO
GPU AMD ASRock RX6600 Challenger D

Mouse Logitech G502
KB Logitech G910
(game set at 250 fps and stable as can be when looking topright corner ingame)

If anyone had a problem similar to this i would like to hear about how OR if it's fixable!
If you need any more info i will do my best to provide with all i can
(note: any info about my previous setup is unknown as i had bought that pc back in the day as is, all i can say is it was running on WIN7, and the GPU was Nvidia but i dont know what model, probably some 1070-1060 is my guess)
Any help would be appreciated, thanks RaadQ.

Bit confused about some of your issues. You're pressing sword and shotgun equip button at the same time? That will not work in GunZ, you have to time your actions perfectly with a (small) delay in-between.

As for your switching during a massive, that "bug" was fixed, you can no longer charge a massive while switching weapons, it will always cancel your massive. Other than this, over the period you mentioned, I have noticed no changes to the way timing for weapon switching works. Perhaps you have muscle memory one way or the other acquired from a different game that allows those instant switching. Stairs slipping is a known annoyance that gets more intense with unstable FPS and/or a high set FPS value. You mentioned that you capped it at 250 which is a good value, but notice how much more intense that effect is when youre on 1000 fps, on the floor too. There isn't really a solution, inclined surfaces are slippery in gunz.