No display and slow windows

OK so first of all here are the PC details.
Processor: i5 3rd gen
Gpu: Amd r9270x 2gb
Ram: 16 GB
Hard : 1 tb

So I bought this PC recently and been using it for 1-2 months.
Now I used to play overwatch at high settings at 100 fps. Or pubg at 60 fps with high settings with no problem.

Now I don't remember what cause it but when I start it the display don't show up. I restart it multiple times by removing CMOS cell or sometime putting it back and it works. So I thought it maybe the cell. Bought a new one but still gave me the same issue.

I was busy on working so didn't focused in fixing the issue. But then sometime when I am playing overwatch or some other game the screen go black. I thought it maybe the GPU driver issue. So I installed the latest driver but it didn't solved the issue but created new issues so I installed the previous driver back.

I thought maybe its overheating
GPU temp was 80 when playing games or 50-55 when doing nothing.
So I reduced the game settings to low.
The display going off kind of resolved for some days I was able to play games at low settings but with 100% render scale.

Although the fps started to go down to 59 at low when I used to get 100 at high on same device.

P.s the black screen at start is not resolved yet. Its still happening and this time I found a better solution rather than removing CMOS. I just restart the PC couple of times while a bootable USB is attached and it start in 3-4 attempt.

I thought maybe its a window issue because I was using window 10 lite version and it was also getting slow day by day.

So I downloaded the latest version from windows website and made my USB bootable. It contains like all type of windows home,pro,business e,t,c.
So I installed windows pro ( cuz its pro so why not)

And now when I start it stays at lock screen for some minutes and don't give option to enter password.
Now after 4-5 minute when it actually gives an option to enter password and j login into the PC.

Well guess what it takes 10-15 minutes to get on the main screen.

My hard is not full BTW so its not a problem.

P.s: remember the no display issue that come at start that required me to restart multiple until the led finally catches the PC and show display. Well its STILL THERE.


So I am kind of tired now. I can't return it as its a custom built. So I want to know which part may be causing the issue or is it software/driver related?