At what temperature does GPU overheat?
You may have an overheating issue if your CPU goes over 60 degrees celsius, or your video card (GPU) goes over 80 degress celsius. If you need to provide us your heat information, please screenshot or type out the listed Max temperatures and which piece of computer hardware they're listed under.
Is 85c too hot for a GPU?
85 degrees is fine. Anything above 90 degrees is not. This should not be an issue as high intensive GPU's and CPU's are meant to heat up to these temperatures while playing games. If you notice that your PC is throttling, stuttering, shutting down, crashing, overheating, etc.