How to make my docker-compose app work?

I tried to make my Django/Vue app work, but I can’t. Here’s the steps: I followed the tutorials to install docker, docker-compose. If I check ufw rules, it shows it allows traffic on port 80, the exct port I need. But if I am inside the droplet, do curl localhost, I get: curl: (7) Failed to connect to localhost port 80: Connection refused I run docker compse up I go to the browser, go to my http://my-droplets-ip, I get “This site can’t be reached” I try to run the kinematic hello world example, from docker hub, it works :-) Obviously, I am a newbie in Docker and first time on DO, but I really want to understand this stuff better. AT this point I am not sure the problem is with my docker-compose file or the firewall. (I doubt it’s the firewall since the kinematic example ran just fine) Here’s my docker-compose file:

version: '3.3'

volumes:
    postgres_data: {}

services:
  backend:
    build:
      context: ./backend
    depends_on:
      - postgres
    volumes:
      - ./backend:/app
    command: /start.sh
    entrypoint: /entrypoint.sh
    restart: on-failure
    env_file: .env

  frontend:
    image: node:10-alpine
    command: npm run serve
    volumes:
      - ./.env:/app/.env:ro
      - ./frontend:/app
    working_dir: /app
    restart: on-failure

  postgres:
    image: postgres:10-alpine
    volumes:
      - postgres_data:/var/lib/postgresql/data
    env_file: .env



  nginx:
    image: nginx:alpine
    ports:
      - "80:80"
    depends_on:
      - backend
    volumes:
      - ./backend/media/:/media/
      - ./backend/staticfiles/:/staticfiles/
      - ./nginx/dev.conf:/etc/nginx/nginx.conf:ro
    logging:
      driver: none