Secure Boot fucked my pc

Hi so basically 2 days ago i turned on Secure boot on my computer because it’s required now to play fortnite tournaments, so i disabled CSM, went to Secure boot but it was already enabled, so i saved went to fortnite and it was saying that it was still off, so i went back to bios disabled Secure boot and enabled it again but this time it asked me for platform keys so i searched that found it and pressed « load default keys » after that i could turn on Secure boot and when my computer restarted i had a black screen, so i tried cmos reset ( both way) and it didnt worked,i tried to boot with minimal hardware, i tried to flash a new bios but i had no light from the qflash led (but my usb led was on when pressing the button) and now i think that my pc is powercycling (not sure), I’ve seen that people fixed it by using a iGPU I have one from another computer compatible so i dont know what to do here is my config: GIGABYTE B550 GAMING X V2 RYZEN 5 5500 16GO RAM GIGABYTE RTX 4060

I Hope someone can help me and excuse me for my poor english