Help, my dual-boot Win/Linux is broken

Have you tried the arch forums? I don't know the exact steps but it'll be something along the lines of booting a linux iso mounting the boot partition, editing grub (assuming you're using grub) and having it see the efi partition/boot stuff (assuming you're using efi) ... but honestly arch or arch related forums might be a better solution. https://forum.endeavouros.com/

I'm not quite sure since I almost forgot everything about it, I was just like first/second try it, but thank you for the help! ill check that forum you just sent me.

Try pressing esc a few times while booting for a uefi boot or hold shift if booting with bios. Assuming GRUB.

Thank you for the reply! Unfortunately, it still doesn't work because on the boot list there is no partition for Linux to boot.

I think EasyBCD could find and add Endeavour as entry into Windows boot manager