Can’t use Xbox on my monitor after bringing it to a associates and altering to 120hz from 60hz

Went to a buddy’s residence to play D4 over the weekend. We had been having problems on his television having it’s locked to 480-620 with the sport solely taking over a fraction of the display. We needed to go in settings and go to the video constancy and overscan space to repair it. The issue now could be that now that I’m residence, my monitor doesn’t help 120hz and I don’t know how you can change it again. Any assist can be appreciated.