First, "How to override (override) the methods of the parent class in the subclass"

This term is called "overloading". It's very simple. First, copy the parent class method intact to the subclass, and then modify the function body. Note that the function signature cannot be changed.

Second, how to call the variable value of the parent class method in the subclass method?

This is impossible. It is impossible to call the local part of another function in a function. variable. It is possible to use the properties of the parent class, because the child class will inherit the public and protected properties of the parent class.