How to create a UserManager for a bulky custom user?

Question

Django

Model

class User(AbstractBaseUser, PermissionsMixin):
    phone = models.CharField(
        max_length=15,
        unique=True,
    )
    sms = models.BooleanField(default=True)
    active = models.BooleanField(default=True)
    staff = models.BooleanField(default=False)
    admin = models.BigAutoField(default=False)
    tutor = models.ForeignKey(
        'self',
        on_delete=models.SET_NULL,
        blank=True,
        null=True,
    )
    TRAINING_ONLINE = 'ON'
    TRAINING_DISTANCE = 'DT'
    TRAINING_FULLTIME = 'FT'
    TRAINING_NONE = 'NN'
    TRAINING_CHOICES = (
        (TRAINING_ONLINE, 'Online'),
        (TRAINING_DISTANCE, 'Distance'),
        (TRAINING_FULLTIME, 'Fulltime'),
        (TRAINING_NONE, 'None'),
    )
    training = models.CharField(
        max_length=2,
        choices=TRAINING_CHOICES,
        default=TRAINING_NONE,
    )
    first_name = models.CharField(
        max_length=50,
        blank=False,
    )
    last_name = models.CharField(
        max_length=50,
        blank=True,
        null=True,
    )
    country = models.CharField(
        max_length=50,
        blank=True,
    )
    city = models.CharField(
        max_length=50,
        blank=True,
    )
    EFFICIENCY_VERY_LOW = '1'
    EFFICIENCY_LOW = '2'
    EFFICIENCY_MEDIUM = '3'
    EFFICIENCY_HIGH = '4'
    EFFICIENCY_VERY_HIGH = '5'
    EFFICIENCY_CHOICES = (
        (EFFICIENCY_VERY_LOW, 'Very low'),
        (EFFICIENCY_LOW, 'Low'),
        (EFFICIENCY_MEDIUM, 'Medium'),
        (EFFICIENCY_HIGH, 'High'),
        (EFFICIENCY_VERY_HIGH, 'Very high'),
    )
    efficiency = models.CharField(
        max_length=1,
        choices=EFFICIENCY_CHOICES,
        default=EFFICIENCY_MEDIUM,
    )
    USERNAME_FIELD = 'phone'
    REQUIRED_FIELDS = ['first_name']

    def __str__(self):
        return self.phone

    def get_full_name(self):
        return self.first_name + ' ' + self.last_name

    def get_short_name(self):
        return self.first_name

    @property
    def is_staff(self):
        return self.staff

    @property
    def is_admin(self):
        return self.admin

    @property
    def is_active(self):
        return self.active

My UserManager

class UserManager(BaseUserManager):
    def create_user(self, phone=None, first_name=None, password=None,
                    sms=True, active=True, staff=False, admin=False,
                    tutor=None, training='NN', efficiency='3',
                    last_name=None, country=None, city=None):
        if not phone:
            raise ValueError('Users must have a phone number.')
        if not first_name:
            raise ValueError('Users must have at least first name.')
        if not password:
            raise ValueError('Users must have a password.')
        user = self.model(
            phone=phone,
            first_name=first_name,
            sms=sms,
            active=active,
            staff=staff,
            admin=admin,
            tutor=tutor,
            training=training,
            efficiency=efficiency,
            last_name=last_name,
            country=country,
            city=city
        )
        user.set_password(password)
        user.save(using=self._db)
        return user

I'm not sure that I wrote UserManager correctly, the most suspicious are setting default values ​​in UserManager (it seems like they are already set in the User module), **extra_fields is used in tutorials and in the official django documentation, how to use it? Thank you very much in advance! I would appreciate any tips and tricks :)