Question Screen freezes and flickers when playing games

[Mohr1]

Hello friends.

I have a problem where my screen will freeze and start flickering after about 30 seconds to 1 minute after I have opened a game.
I thought it was my GPU so I got it replaced by NVIDIA, and I just installed the new GPU today but I still have the same problem

But the weird part is that when I was waiting for my replacement I decided to use my old GPU, GTX 970, and when I played games on my GTX 970 I had no problem

Oh and also I don't know if it is the right forum to post in but I figured that since I got my GPU replaced it couldn't be my GPU that was the problem so I thought maybe my motherboard, that's why I posted in here

Could it be my PSU? since it worked fine with my GTX 970 which doesn't need as much power as my RTX?

Specs
My PSU is an Energon EPS-750W
https://www.inter-tech.de/en/products/psu/atx/eps-750 - Link to my PSU

A video of what happens when the screen freezes and flickers



Thanks for the help in advance :=)

 

[Mohr1]

Okay so I have done a little more digging, and it turns out that I can play League of Legends just fine without any problems, but when I try to go into a game that is a bit more heavy on the GPU, like Rainbow Six Siege, the game crashes if I have all the settings on very low, and when I have all settings on ultra the whole PC freezes.