As stated in the title my PC suddenly completely shuts down as if i would lose power. I am pretty sure that it is the Power supply but i wanted to ask if it even is possible for a CPU or GPU to just let the whole computer lose electricity before i buy a new PSU
Few things to check:
make sure all wires are secure and snuggly attached to everything. Including the rest/power button switches.
double check temps before crash to see if theres any issues while idle or under load there.
check and possibly post your windows logs and event viewer logs to look for possible issues leading up to right before the power fail events.
do you have any overclocks applied? (Including xmp/amp) if so set your motherboard back to defaults and test again.
make sure BIOS firmware is up to date (might as well make sure all your other drivers are up to date as well).
try each ram dimm one at a time in both primary slots, this may help determine a dimm issue.
Borrow or using another power supply would be the best way to full confirm or deny the issue being a power supply failure. When a computer just instantly powers off like that its usually either a power failure or some kind of critical harware failure hitting a failsafe and shutting down.