Fortnite Xbox one cursor instead of controller?

I have a huge problem. Yesterday I changed something unintentionally with the Fortnite settings. Now I'm shown a mouse pointer / cursor in the start screen of Fortnite. Unfortunately, I have no mouse and no keyboard. I can't do anything with the controller, or operate the cursor. How can I reset this setting and how did I switch to a mouse control at all?

Already done: works only if you connect a mouse and change the setting again