I accidently rebooted during pacman update and now my system dosen't show option to boot into endeavour os. Systemd just shows option to boot into firmware interface please help!

I've lost everything and I don't know how to get it back. How can I repair my system all I have is a usb with slax linux. I am freaking out because I had a lot of projects on their that I hadn't pushed to github as well as my configs and rice. Is there any way to repair my system? Can I get a shell from systemd?