i dont know how to fix this error
This is really a question about C#, not Unity. If the problem isn’t readily apparent from the error message, then you should invest in learning C#. I suggest HackerRank for that purpose.
Anyway. In simplified terms, a C# method looks something like this:
ReturnType Name(ParameterType1 parameter1, ParameterType2 parameter2, ...)
{
statement1
statement2
...
}
The ReturnType is the kind of thing that the method returns when it exits. There is a special return type called “void” which means “this method doesn’t return anything”. You can have as many or few parameters as you like but each one must have a type and they all must be assigned.
If you didn’t write PlayerController.cs, then you should take this up with the person who did.