HELP! How do I get my Mac back?

How do I get my Mac to load properly?

Can’t get my Mac to load properly. Stuck on this screen. For context, this Mac is 10 years old, but recently used open core to upgrade to newest OS. Was working great until the thing tried to upgrade again without backing up. No matter what I try, I cannot get past this screen. Just want to be able to use my computer again. Any advice? Any help would be much appreciated. Thanks!