Don't come to the bios?

So I was in Fortnite with my buddy half an hour ago but all of a sudden I had a blackscreen except for a small rectangular box in the lower left corner so then I turned off the pc and started my pc again and then came a rock sign from the bios I come but not in win10 and if I want to go into the bios it doesn't work what should I do

That's this screen with the rectangle

Turn it off and unplug it. Wait a bit and plug it in again → try to start.

select boot menu → F8 or F11 → hard disk

BIOS → F2

I now come to the bios but win10 starts net