Pc Crashing Mid Game to Blue Screen

[aerman]

Hello!

My pc which is a bit old has been lately running into a problem. It started while playing overwatch/ witcher 3 and it would crash to a black screen. After restarting my pc often everything would be back to normal. But sometimes after a crash my gpu would not be detected and the windows resolution would be really low, then i had to restart again to fix that issue. But this time after gaming my pc went to blue screen. So basically i can`t game on my pc because the crashes are so frequent.
  I have tried troubleshooting. I used Windows Memory tool and no errors. I also used windows error checking for my hard drives, also no errors. But when i ran seagates own hard drive program, one of my hard froze on the long generic tests. (Pictures in the attachments). Could my hard drive be causing this issue or is it something else. Also how should i start fixing this problem? Thanks in advance!