Fortnite stretches with 2 monitors play?

I have a problem and although I have two monitors one is 16: 9 and the other 4: 3. I convert my resolution and 1440x1080 (Stretcht)

As soon as my game opens on the 16: 9 monitor everything seems to work, but my mouse is moved (ingame I'm eg On but the game thinks I'm still playing 16: 9 and I'm not ready for it, but a piece further down on the left)

Do I have to change something in my settings, if so what

I'm grateful for any help

Go to your desktop and make a right click. Then change the monitor resolution (may be Intel or Nvidia) to the resolution you want to finally play with. It is important that you select the item "Scale fullscreen".