Question Please help with failing system

Aug 19, 2020
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Hey guys so basically i built a computer a few months back, the specs are

b450 elite mobo
ryzen 5 3600
16 gb ram
5700xt

Basically, while playing ark and pubg which were the only games i was playing it would randomly crash every 2 hours or so, i took it to the shop i bought it from and they said it was probably a loose ram stick and said they left it running overnight with valley benchmark and it ran fine so it should be ok, so i played ark again and it crashed, i called them and they said it was probably a software issue and to reinstall windows, so i did.

After that it now greenscreens and reboots every 5 - 10 minutes even while in windows not gaming. I have taken it back to them but it will be 2 weeks before they can look at it again, im afraid there will be no progress made and basically i have wasted a bunch of money.

Is it acceptable that this is happening? Could i have broken something while building it myself as this is my first time building.

Does anyone have any advice for me?? please help and thanks for your help