Time Machine Backup not letting me access my files.

Recently I got a brand new M4 Mac mini to replace my old iMac. So, obviously I wanted to transfer my data. I plugged in an external drive and backed it up. Since my iMac had more storage than my Mac mini, my backup had 300 gb and my Mac mini only has 256. So I decided to just keep the files I needed. Instead of Restoring the whole backup, I dragged my files over. But for whatever reason, it acts as if I don't have permission to open the files. Every time I move or rename a file, it makes me enter my password (I.e. an administrator password) Now, that's fine. But if I try to edit a file for example if I open a pages file and try to edit it, it says I need to duplicate it if I want to edit it. Even when I duplicate it, it still doesn't let me edit. It also even does this for minecraft worlds if I try to launch it, it will say failed to load world. For the important documents I can just copy the text, but I still want to figure out what is happening.