Need help with Django models

I need a user foreign key inside a user model
It’s been giving me errors for hours now

We can’t really begin to guess what is wrong without seeing your code.

class User(AbstractBaseUser, PermissionsMixin):
   name = models.CharField(max_length=255, default='John Doe')
   sitter = models.ForeignKey(
   sitter_appointment = models.ManyToManyField(
   through_fields=('pet_sitter', 'pet_owner')

class Booking(models.Model):

 start_date = models.DateTimeField()  
 end_date = models.DateTimeField()
 owner_of_pet = models.ForeignKey(
     on_delete=models.CASCADE, blank=True,null=True)
 sitter = models.ForeignKey("User",related_name="sitter_bookings", on_delete=models.CASCADE)

class BookingSerializer(serializers.ModelSerializer):
   pet_sitter = UserReadSerializer()
   pet_owner = UserSerializer()
   class Meta:
       model = Booking
       fields = ('id','start_date', 'end_date', 'sitter', 'owner_of_pet','sitter_id')

I added the code.
Basically we wanted to create an appointment between a user which is the user that is signed in and another user in the database