Software update is trying to authenticate user – M1 problem

Hello, I am trying to migrate data from my old MacBook Pro into the new MacAir M1 laptop. First of all, I'll get this message on Migration assistant: "This Mac can't be used to migrate data. Due to an issue with unlocking this system, you can't migrate. Please update this Mac and retry." But when I am trying to upgrade MacOS Big Sur 11.3.1 to 11.5.2, the update downloads but when I try to install it says "software update is trying to authenticate user". And this is when the trouble starts. My password is not accepted. I do use the correct password and I can sign in to the computer with it. Yes, I have read that there are plenty of people who have this same problem and I have taken all the steps I have found so far from using safe mode to configuring user accounts. I have the admin status. I even tried to reinstall macOS, but I get this notification: "Recovery is trying to change system settings. No administrator was found." Could you please help me out with this one. Thank you!