Fortnite streched new season?

Today the new season started in Fortnite and if I want to set my streched resolution after the update in the "full screen in the window" mode, I'm told that the resolution of the game must correspond to the resolution of the monitor. I have set everything correctly in my system control and in the data files, but it doesn't work?

does anyone have any idea what could be wrong?

If you want to change the resolution it has to be full screen I think

Then it looks very strange