Permissions problem

2018 Mac Mini (Macmini8,1) 3.6 GHz Quad-Core Intel Core i3 MacOS 13.6 Ventura My internal Macintosh HD Get Info says I can only read. Obviously this is not correct, because I do read and write to the drive all the time. Permissions: system Read & Write; wheel Read Only; everyone Read Only. When I try to change them to Read & Write, or add users, I get an error message saying The operation can’t be completed because you don’t have the necessary permission. What is going on, and how can I fix this problem?