GTX 960 game cutouts

[Scpholicz]

Whenever i try to play a certain game on pc (not always demanding as i can play forza horizon 4 without a single problem but not fifa 19) it seems to just cutout to a blue screen completely, this has happened multiple times, however once i change my gpu fan to about 70% fan speed (msi afterburner) and turn everything down to the bottom, core clock memory clock etc, it seems to work significantly although does still sometimes crash, i would lead to believe that this is a cooling or a psu problem, i do have a dodgy 500w power supply and that may be dodgy but i feel this may not be the problem as it could also be cooling within the graphics card (leading to why i have to ramp the fan up so high) however once again while i feel one of the problems is the cooling sometimes the card isnt even hot and it crashes, which then makes me think that its the power supply, but why do i need to ramp the fan speed up?, this whole thing is confusing and i usually know whats going on inside my pc but not this time way to confusing 

[Lightning44]

What does Afterburner say about your GPU temps? Have you tried updating the drivers ? If anything, try dismantling your gpu and replacing the thermal paste.