Monitor keep going black mode again and again

I was trying to adjust the brightness in my girlfriend monitor I tried everything I searched everything in windows might be the latest version I can find the option to adjust the brightness so I see this option (HDR) I have no idea what that means I am not very sure if it’s safe to turn on or off and there this other option night light I turned them both at once I keep turning hdr on and off for a couple of times played a game it’s was fine I had like 3 hours of use of the computer I had to go to school my girlfriend continued to use the computer and suddenly now I turned everything on checked the cables if there were lose it was fine had to even count to 15 seconds on every button.

I have to turn on so the pc has the time to process everything I don’t know about the fans and stuff and I see the monitor going black randomly I need to fix this now or else I will be in trouble with my girlfriend. Once the computer was going black randomly I searched some stuff again how to fix this problem I currently have I reset the pc 2 times it’s still like this I gave it time to cool it wasn’t even warm or hot it might be something about the off and on Hdr while I am typing these monitor still going black randomly I can’t get any help.

I have watched a couple of videos on youtube Google isn’t giving me information there are many ways to fix it but I am not sure if it will work it may make the monitor go worse. I can’t trust youtube and Google the information they have given me might not work it might just make the computer worse I am willing to restart the pc again. the monitor just turned off by itself it said (no connection/signal) the monitor is N vision please I need a way to fix this.