Reinstalling OS

Ok so I messed up trying to downgrading from Catalina to Mojave. I probably touched wrong spot on HD. I also deleted OS which was running at the time, Catalina.

Now when I restart with command + R, I can’t even re-download Catalina. No time machine, only iCloud backup. I don’t mind starting clean, most likely that’s the only option anyway. I really didn’t like Catalina but right now I just want a running machine so if I can find a way to reinstall Catalina it’d be great. Mojave preferred. Pls help!!

I have another MacBook (2018) and MacBookPro with Sienna.

Thank you very much for your help.