What should models.py look like for chat?

Question

Django

I make a social network for educational purposes. Here I read about how the database structure for a chat should look like.
This is what my models.py looks like

from django.db import models

# Create your models here.
class User(models.Model):
    first_name=models.CharField(max_length=40)
    second_name=models.CharField(max_length=40)
    class Meta:
        db_table="users"
class Message(models.Model):
    to_id=models.ForeignKey(User,on_delete=models.CASCADE,related_name="reciever")
    from_id=models.ForeignKey(User,on_delete=models.CASCADE,related_name="sender")
    content_id=models.AutoField(primary_key=True)
    class Meta:
        db_table="messages"
class MessageContent(models.Model):
    message=models.ForeignKey(Message,on_delete=models.CASCADE)
    content=models.TextField()
    class Meta:
        db_table="contents"

Did you implement the structure for the chat correctly? Is the content_id needed or does the Message id replace it?