Black borders in game and on desktop

Hey,

I'd like to get rid of that vertical right black border on my screen. I searched on the internet how to do that but seems like I can't.

I'm using a NVIDIA card. I do have a 4:3 screen and using @desktop and @ET a 4:3 resolution

When I choose, as said in the internet, "Full-screen" in "Adjust Desktop size and position" and "perform scaling on : GPU" + check "Override the scaling mode set by games and programs, I can't go higher than 85hz because I had to personnalize it to get 120hz (otherwise NVIDIA is not showing any higher values) BUT THERE IS THE PROBLEM, when I check all I just said, my resolution come back to 85hz and when I launch the game, I still have the black borders because I don't have the same hz in ET and desktop.

So the question is: How can I do not to have those black borders @desktop while using 120hz OR how can I do not to have black borders in game, simply?!

Cheers

P.S : for those who haven't understanding yet, I CAN'T PUT THE DESKTOP AND GAME WITHOUT THE BLACK BORDERS @120HZ cause NVIDIA takes the higher hertz (85hz) in the known resolutions and to get 120hz I had to personnalize it.