macOS reinstallation doesn’t work

Hello.

i’ve had problems installing macOS updates for several months, this was a problem for me as I needed apps like microsoft word for school.

When I tried to update any macOS updates, it never worked - after an update I always restarted the computer, but the update showed up again..

So I turned off my mac and turned it on on safe mode and went to reinstall the whole macOS. But unfortunately for me - it doesnt work (: now I just cant turn on my whole macbook, because when I try to reinstall the macOS, there’s always an error saying “Failed to apply the software update. Please try again.”

it always shows up after like 4 hours (!) of reinstalling. I tried it like 5 times and the same error ir still showing up…

how can I repair it? :(