Is my code OOP and what could i do better?

[BashBedlam]

Do you have an idea how to fix the number 8 i've been trying multiple things and its still not working?

Yes, sinceBücheris aLibraryclass, you just need to initialize it that way. Try it like this and notice line 3.

class Bücher(Library):
    def __init__(self):
        super ().__init__ ()
        self.borrowBooks = []
 
    def displayUnavailableBooks(self):
        print("Liste mit ausgeliehenen Bücher: ")
        for books1 in self.books1: 
            print(" -" + books1 )