Python classes

[Python_User]

Ok, this is a bounce of information and difficult to understand.

class Doubleup:
    classvar = 'Hello'
    classvar = 'Goodbye'
     
    def __init__(self):
        self.punctuation = ','
        self.punctuation = '!'
 
    def __init__(self):
        self.punctuation = ';'
        self.punctuation = '?'
 
    def message(self):
        return f'Hello world{self.punctuation}'
 
    def message(self):
        return f'Goodbye world{self.punctuation}'
 
print(Doubleup().message())

From the code above:
- Why isn't the puntuaction defined as argument in the methods?
- What is the function of "f" in return f'Goodbye world{self.punctuation}'?
- What is the curly brackets function in return f'Goodbye world{self.punctuation}'?
- How knows python to refer to the question mark?? This is really difficult to understand for me at the moment...

Maybe the questions are dumb, but I am trying to understand it properly.