Question PC freezes , stutters(lag), green screen

[vortex123]

My pc sometimes wont boot and goes into the bios or just wont respond but when it does boot it is laggy af , cursor keep getting stuck, and there are random green flashes on the screen and the hdd light is on constantly . i replaced my hdd because it stopped working.
my pc specs:-
CPU - i5 6400
GPU - amd sapphire rx 470
MOBO - gigabyte b450m
HDD - seagate barrcuda 2tb
PSU - cheap no name 500 watt

 

[rgd1101]

replace the psu?
check cpu/gpu temp?

 

[vortex123]

replace the psu?
check cpu/gpu temp?

GPU and cpu temp are okay , I ordered a new psu