I can't get into 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?

Test the F keys at startup. Mostly F12

No keys work

Or that's not the case sometimes