Why Fps Problems in Fortnite Chapter 2?

I've had big problems with my Fps in Fortnite lately. I actually have good specs in my PC, including an Rx5700 xt overclocked, a Ryzen 5 3600 also oc and Fortnite is stored on an M.2 SSD. Actually I'm used to play at 144 Hz, with DirectX 11, all settings on epic (except for shadows, which are off), Vsync on and 1080p. Lately, however, I have had extreme fps drops and generally always below 90 fps. Funny thing is that my system runs very well based on benchmarks and other games and only Fortnite doesn't work.

I had something like that, it helped me to uninstall the game and then reinstall it. Otherwise maybe. Start the game as administrator

I have an R 7 3700X and a 2070 Super, but I still sometimes have creative fps drops to 40 for a few minutes when I move my mouse. I have no clue what's the cause of this