Question My pc crashes when I got a new monitor.

Jun 30, 2019
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I got a BenQ - G2420HDBL 24.0" 1920x1080 Monitor and after that my games start to crash.

I mostly play LoL at medium settings and 60 fps. This may happen instantly or after an hour of playing but when it does my screen becomes colorful with green pixels and frozen while the speakers make a buzzing sound and after that the programs crash. But when I lower the settings to lowest and go 30 fps my pc never crashes. what could cause this?
The monitor or my GPU or even the power supply?
Did I even post this question correctly idk. I'm just desperate and want to fix my pc. Hope you can help!
my pc parts:
https://pcpartpicker.com/list/VGHtP3