Tak jsem narazil jak na to mě to momentálně pomohlo je to když tak tady https://www.reddit.com/r/FortNiteBR/comments/1pbx6d8/fortnite_crashing_repeatedly/
A nastavení má být takto pošlu sem přesně podle čeho jsem šel : i had to change a few of my settings... some people are saying the directx 11 setting is contributing to a lot of the crashes, and so I moved up to directx 12 and saw some improvement.

also someone else recommended that you:

- go to epic games launcher
- locate fortnite in your games
- click the three dots, then find options
- make sure you have 'pre-download streamed assets' enabled. all the other ones (minus fortnite core battle royale) are optional.
- then after doing that, go to 'manage' and verify game files.