Question Windows Crashing/ Black Screen/ Freezing

[testeras]

My spec
mb ih61m, i5 2320, Rx 550 4gb, 2x4 ram 1333, psu 450w.
Every part is bought used expect gpu which is new 2 months old.
Sometimes when im playing games (mostly in scp secret lab) screen would sometimes go black or the screen will entirely freeze and wont come back until i restart pc. Also it happened sometimes screen freezing while system is idling doing nothing. Gpu is 3.0 8x while working on 2.0 x8 with pcie security patch broken. Black screen happened once 1 month ago but now is becoming frequently

 

[Lutfij]

psu 450w
Make and model of your PSU and it's age?

What OS are you working with? Where did you source your installer for the OS?

 

[testeras]

psu 450w
Make and model of your PSU and it's age?

What OS are you working with? Where did you source your installer for the OS?

450 W Falcon FLC-450L 3 or 4 years old (and its mine psu not from that person)
Windows 10 Home, Os came with pc i bought from random person who sent me shipment

His pcu was AcBel Polytech pca246 but his gpu died while i was using it so i bought new gpu and switched psu to falcon

 

[testeras]

I was looking inside of pc for 2 hours then i saw that gpu was not fully plugged in so this shoud fix problems.