Your class is player but the constructor is Player, because they are different it is expecting Player to be a method rather than a constructor
Change the class name to Player and you will be good
Your class name is player with lower case. When the compiler finds the constructor for class Player (upper case), it thinks it is a method called Player without a return type specified.
So simply rename your class to uppercase Player. C# is case sensitive, so player and Player are two different things.