Fortnite Stretched has black edges?

I try to play Fortnite on 1440 stretched, but I always get black edges on the monitor. I changed the game files, the monitor settings, the amd settings and the fortnite settings correctly and closed the game during that, how do I get rid of those edges?

If the black edges are big, it's probably because the game can't be played in Ultrawide. I do not know exactly because I do not play fortnite myself, but could be

You have to start fullscreen on NVIDIA.

At 3:00 min