PC constantly crashing/freezing/not working at all.

I bought my PC about three weeks ago and it has been working perfectly fine until yesterday. I downloaded the NVIDIA app from the official website to adjust a few things for my gpu. When I started Fortnite, my frames dropped heavily. I deleted the app and adjusted a few settings to optimize performance and graphics but that just made my PC look awful so I set everything back to normal. Then I wanted to play Battlefield 6 and went into my bios to turn on safe boot. Ever since then my computer has been freezing, crashing and running very slowly non stop. The only thing that works halfway decent is google. I set everything I changed in my bios and everywhere else back to normal and nothing works, even the power button on my PC doesn’t work sometimes