I need help with my Mac Mini

Well my Mac Mini was slow. So I formated it. When I was creating a login for the computer, the energy fell, I was like “oh okay then I will wait it to return” then after it returned it was like if I already set it up. I said “oh okay I’ll just put the password that I chosen” it did not work. Then I tried to reset it from my iCloud but It did not work it seems that it’s not in my iCloud but it’s appearing there, so I’m stuck with a Mac Mini that has a password witch is not the one that I have chosen and my iCloud can’t reset the password. If anyone can help before I bring it to an thecnical assistance I’ll be grateful

Thanks!

I finally got it unlocked but now I have another problem.

It’s in Portuguese because I’m from Brazil. So it’s now saying “the version of macOS in the disk selected needs to be reinstalled, Use the recuperation tool to reinstall macOS or select another disk to initializate”

Then there is two buttons the first one “recuperation” and the other one “disk initiation”

Thank you guys so much for help, today I’ll bring the Mac Mini to an Apple Store to see if they can fix it, again thank you so much for the help!