How to display last 25 messages in a chat application in Django

I am building a chat application in Django. But I have a problem with displaying the last 25 messages of my chat. Here is my code.... This is my model for saving the messages:

from django.contrib.auth import get_user_model
from django.db import models

class Message(models.Model):
    username = models.CharField(max_length = 255)
    room = models.CharField(max_length = 255)
    content = models.TextField()
    date_added = models.DateTimeField(auto_now_add = True)

class Meta:
    ordering = ('date_added', )

Here is the function that should filter the messages and render the template in views :

@login_required(login_url = 'index')
def room(request, room_name):
    messages = Message.objects.filter(room = room_name)[:25:]
    return render(request, 'chatroom.html', {
        'room_name': room_name,
        'messages': messages
    })

Here is the part that should display the messages in chatroom.html template:

      <div class="container_chat">    
        <form>
            <div class="textarea" id="chat-text" rows="10" readonly>  </div> 
            <div class=container_chat_inputs>
                <input id="input" placeholder="Enter a message" type="text"></br>
                <input class="chat_message_submit" id="submit" type="button" value="Send">
            </div>
        </form>
    </div>

And here is my function for saving the messages in the model in consumers :

    @sync_to_async
    def save_message(self, username, room, message):
        Message.objects.create(username = username, room = room, content = message)

So far I believe that the main problem is in the filtering in views. Right now it only seems to display the first 25 messages. I tried reversing the slice, but Django does not support negative slicing. I also tried reversing the ordering, which does display the last 25 messages, but of course in a reversed order.

Question: How do I fix this? How do I display the last 25 messages?