docker-compose and persistent storage problem

I’m new with docker and docker-compose, and I have issue with persistent storage. I have three folders that I need to keep files outside of docker. I don’t know what I’m doing wrong.

docker-compose.yaml

version: '3.3'

services:
    webserver:
        build:
              context: ./
              dockerfile: webserver.DockerFile
        ports:
            - 80:80
            - 443:443
        volumes:
            - html:/var/www/html
            - platforms:/var/www/platforms
            - sites-available:/etc/apache2/sites-available
    mysql-server:
        image: mysql:8.0.20
        restart: always
        environment:
              MYSQL_ROOT_PASSWORD: somepassword555

    phpmyadmin:
        image: phpmyadmin/phpmyadmin:5.0.1
        restart: always
        environment:
                PMA_HOST: mysql-server
                PMA_USER: root
                PMA_PASSWORD: somepassword555
        ports:
                - "8080:80"

When I run build on this, I get empty folders in webserver. Folders on host are not empty.

Source: Docker Questions