Login screen having issues

Whenever i start my laptop, the login screen does not show me in full resolution. the login screen shows in (4:3) but after i login my screen goes back to normal which is (16:9). Anybody know how i can solve this?

i tried this i got the details from arch wiki.

i made my own 90-monitor.conf
Section “Monitor”
Identifier “”
DisplaySize 345 194 # in millimeters
Display size i kept my laptops resolution. but didn’t workout

thanks in advance