MongoDB Data loss after a day

I have a docker project with Mongo DB, after a day or two…I keep losing the data

  mongodb:
    image: mongo:latest
    container_name: mongo
    ports:
      - "27017:27017"
    volumes:
      - data:/data/db
  mongo-express:
    image: mongo-express
    container_name: mongo-express
    ports:
      - "8081:8081"
    environment:
      - ME_CONFIG_MONGODB_SERVER=mongodb

volumes:
  data:

what is the problem? and how can I solve it? thank you!