Dual boot problem and black screen

Hi, I'ven using Windows 10 and Linux in a dual boot for 2 months, but yesterday when I turned on my pc, it just directly booted to windows 10, and the "menu" that always appeared that let me chose which OS I wanted to use isn't there anymore.
also, i don't have access to the bios, when I try to enter the screen, it just turns black.
(I have already tried reseting the cmos in every way I could)
after searching a way to fix it, I realized that it could be the fast boot option that I deactivated but the problem persists.
later, I managed to boot to Linux via command but after that, it does the same just that now I can only use Linux, and boots to Linux every time I turn on the pc.
and then when I tried to use linux boot repair my pc only displays a black screen with no acces to bios, recovery environment and can't even use a usb with windows 10 to try to reinstall windows or repair it
If anyone knows what happened or had the same problem, please let me know a way to fix it, thanks