Nginx Proxy Manager Bad Gateway (Docker WordPress and Nextcloud)

I’ve a Raspberry at home and I try to run the Following setup :

• Nginx Proxy Manager (jc21/nginx-proxy-manager) as reverse proxy to acces
• Portainer (portainer/portainer-ce)
• WordPress (docker official image)
• Nextcloud (docker official image)

It’s working really well for portainer but for the other two I get a Bad Gateway Error (https and also http).

I’ve found some solutions on the web but none of them work for me + all of them was "do this, this and this" solutions. I want a real understanding of what going on and how to fix this.

I link the docker-compose files that I use and screens for the conf in Nginx Proxy Manager.

Thanks for your help !

Nginx Proxy Manager

    version: "3.8"
    networks:
        dockerpi:
        external: true
    services:
    npm-app:
        image: "jc21/nginx-proxy-manager:latest"
        ports:
        - "80:80"
        - "81:81"
        - "443:443"
        environment:
        DB_MYSQL_HOST: "npm-db"
        DB_MYSQL_PORT: 3306
        DB_MYSQL_USER: "npm"
        DB_MYSQL_PASSWORD: "npm"
        DB_MYSQL_NAME: "npm"
        volumes:
        - ./data:/data
        - ./letsencrypt:/etc/letsencrypt
        networks:
        - dockerpi
    npm-db:
        image: "jc21/mariadb-aria:latest"
        environment:
        MYSQL_ROOT_PASSWORD: "npm"
        MYSQL_DATABASE: "npm"
        MYSQL_USER: "npm"
        MYSQL_PASSWORD: "npm"
        volumes:
        - ./data/mysql:/var/lib/mysql
        networks:
        - dockerpi

Portainer

    version: "3.8"
        networks:
            dockerpi:
            external: true
        services:
        portainer:
            image: portainer/portainer
            privileged: true
            ports:
            - "8000:8000"
            - "9000:9000"
            volumes:
            - "./data:/data"
            - "/var/run/docker.sock:/var/run/docker.sock"
            restart: always
            networks:
            - dockerpi

Nextcloud

    version: "3.8"
    networks:
        dockerpi:
        external: true
    services:
    nextcloud-db:
        image: mariadb
        restart: always
        command: --transaction-isolation=READ-COMMITTED --binlog-format=ROW
        volumes:
        - ./db:/var/lib/mysql
        environment:
        - MYSQL_ROOT_PASSWORD=nexcloud
        - MYSQL_PASSWORD=nexcloud
        - MYSQL_DATABASE=nextcloud
        - MYSQL_USER=nextcloud
        networks:
        - dockerpi
    nextcloud-app:
        image: nextcloud
        restart: always
        ports:
        - 8010:80
        - 9010:9000
        links:
        - nextcloud-db
        volumes:
        - ./nextcloud:/var/www/html
        environment:
        - MYSQL_PASSWORD=nextcloud
        - MYSQL_DATABASE=nextcloud
        - MYSQL_USER=nextcloud
        - MYSQL_HOST=nextcloud-db
        networks:
        - dockerpi

WordPress

    version: "3.8"
    networks:
        dockerpi:
        external: true
    services:
    wp-test:
        image: wordpress
        restart: always
        ports:
        - 8020:80
        environment:
        WORDPRESS_DB_HOST: wp-test-db
        WORDPRESS_DB_USER: exampleuser
        WORDPRESS_DB_PASSWORD: examplepass
        WORDPRESS_DB_NAME: exampledb
        volumes:
        - ./wordpress:/var/www/html
        networks:
        - dockerpi
    wp-test-db:
        image: mariadb
        restart: always
        environment:
        MYSQL_DATABASE: exampledb
        MYSQL_USER: exampleuser
        MYSQL_PASSWORD: examplepass
        MYSQL_RANDOM_ROOT_PASSWORD: "1"
        volumes:
        - ./db:/var/lib/mysql
        networks:
        - dockerpi

ps: I don’t post the screens because it’s seem I can not post images now.