So, I used a GPU OC tool and I kinda maxed it out, games were running nice, but outta nowhere my pc starts running slow and CS:GO goes from like 190FPS to 90FPS. It doesn't seem damaged, I don't know what to do...
follow these steps. start with a simple overclock without increasing voltage and get that stable, once thats done you can maybe look at increasing voltage.
Also google the safe max speed of your GPU, there will be guides as to what you can expect to hit.