reducing the size of a Django/mysql docker image

I am currently using this Dockerfile to build my backend service:

FROM python:3.9-buster
ENV PYTHONUNBUFFERED 1
WORKDIR /app
COPY requirements.txt /app/requirements.txt
RUN pip install -r requirements.txt
COPY . /app
CMD python manage.py runserver 0.0.0.0:8002

I also have a mysql database the Docker-compose file is:

version: '3.8'
services: 
    dj:
        build: 
            context: .
            dockerfile: Dockerfile
        ports:
            - 8000:8002
        volumes: 
            - .:/app
        depends_on: 
            - db
    db:
        image: mysql:5.7.22
        restart: always
        environment: 
            MYSQL_DATABASE: ...
            MYSQL_USER: ...
            MYSQL_PASSWORD: ...
            MYSQL_ROOT_PASSWORD: ...
        volumes:
            - .dbdata:/var/lib/mysql
        ports: 
            - 33068:3306    

I want to reduce the size of my container which is currently 1.2G any detailed explanation on how to do that would be helpful, precisely I want to know how to do a multisatge build or use a lighter base image properly because I looked at some blogs that use the alpine as their base image but that doesn't work for me probably because my requirement.txt:

Django==3.1.3
djangorestframework==3.12.2
django-cors-headers==3.5.0
djangorestframework-simplejwt==4.7.1
pyjwt==2.1.0
mysqlclient==2.0.1
django-mysql==3.9

is not enough.