Nextcloud Docker compose SubPath URl

Hey guys,
I hope someone can help me with my setup.
I have just started with nextcloud a month ago and have just learned the basics so pls be kindful.

I have my Nextcloud allready up and running. My problem is it is running under “https://myurl.com/” but i want it to run under “https://myurl.com/SomeOtherName/” for example “https://myurl.com/nextcloud/”.
Yes i already searched for this and yes i found all the forum posts where someone with the issue fixed his or her problem.

My underlying problem, I think, is that i dont know how to stop my jwilder/nginx-proxy:alpine from changing/recreating the default.conf in my docker container in /etc/nginx/cond.d/ everytime on startup. Therefore I cant configure my proxy.

Maybe someone could give me a hint on this or maybe someone who knows dockerized nginx reverseproxy configurations could explain me how to fix this.

Thanks in advance

docker-compose.yml

version: '3.5' 

services:

  proxy:
    image: jwilder/nginx-proxy:alpine
    labels:
      - "com.github.jrcs.letsencrypt_nginx_proxy_companion.nginx_proxy=true"
    container_name: nextcloud-proxy
    networks:
      - nextcloud_network
    ports:
      - 80:80
      - 443:443
    volumes:
      - ./proxy/conf.d:/etc/nginx/conf.d:rw
      - ./proxy/vhost.d:/etc/nginx/vhost.d:rw
      - ./proxy/html:/usr/share/nginx/html:rw
      - ./proxy/certs:/etc/nginx/certs:ro
      - /etc/localtime:/etc/localtime:ro
      - /var/run/docker.sock:/tmp/docker.sock:ro
    restart: unless-stopped
  
  letsencrypt:
    image: jrcs/letsencrypt-nginx-proxy-companion
    container_name: nextcloud-letsencrypt
    depends_on:
      - proxy
    networks:
      - nextcloud_network
    volumes:
      - ./proxy/certs:/etc/nginx/certs:rw
      - ./proxy/vhost.d:/etc/nginx/vhost.d:rw
      - ./proxy/html:/usr/share/nginx/html:rw
      - /etc/localtime:/etc/localtime:ro
      - /var/run/docker.sock:/var/run/docker.sock:ro
    restart: unless-stopped

  db:
    image: mariadb
    container_name: nextcloud-mariadb
    networks:
      - nextcloud_network
    volumes:
      - db:/var/lib/mysql
      - /etc/localtime:/etc/localtime:ro
    environment:
      - MYSQL_ROOT_PASSWORD=
      - MYSQL_PASSWORD=
      - MYSQL_DATABASE=nextcloud
      - MYSQL_USER=nextcloud
    restart: unless-stopped
  
  app:
    image: nextcloud:latest
    container_name: nextcloud-app
    networks:
      - nextcloud_network
    depends_on:
      - letsencrypt
      - proxy
      - db
    volumes:
      - nextcloud-html:/var/www/html
      - ./app/config:/var/www/html/config
      - ./app/custom_apps:/var/www/html/custom_apps
      - nextcloud-data:/var/www/html/data
      - ./app/themes:/var/www/html/themes
      - /etc/localtime:/etc/localtime:ro
    environment:
      - VIRTUAL_HOST=my.url
      - LETSENCRYPT_HOST=my.url
      - LETSENCRYPT_EMAIL=me@my.email
    restart: unless-stopped

volumes:
  nextcloud-html:
    external: true
  nextcloud-data:
    external: true
  db:

networks:
  nextcloud_network:

As one can see i have a mariadb Nextcloud with a nginx reverse proxy and letsencrypt ssl certification combined in a virtual network. The data volumes are lying external on my 8TB Raid 5 for data loss protection.

My config.php is pretty basic just some tweaks for mail stuff and so on.

Okay after more then a week of struggle with this I finally found an solution.
I found this: Solution
My docker-compose.yml changed slightly and I lost all my data due to my fault deleting my user DB but it works now.
Her are the nessecary files.
docker-compose.yml

version: '3.9'

services:
  proxy:
    image: jwilder/nginx-proxy:alpine
    container_name: nextcloud-proxy
    restart: unless-stopped
    networks:
      - nextcloud-network
    volumes:
      - ./proxy/conf.d:/etc/nginx/conf.d:rw
      - ./proxy/vhost.d:/etc/nginx/vhost.d:rw
      - ./proxy/html:/etc/nginx/html:rw
      - ./proxy/certs:/etc/nginx/certs:ro
      - /etc/localtime:/etc/localtime:ro
      - /var/run/docker.sock:/tmp/docker.sock:ro
    ports:
      - 80:80
      - 443:443
    labels:
      com.github.jrcs.letsencrypt_nginx_proxy_companion.nginx_proxy: "true"

  db:
    image: mariadb
    container_name: nextcloud-mariadb
    restart: unless-stopped
    networks:
      - nextcloud-network
    volumes:
      - db:/var/lib/mysql
      - /etc/localtime:/etc/localtime:ro
    command: --transaction-isolation=READ-COMMITTED --binlog-format=ROW
    environment:
      - MYSQL_ROOT_PASSWORD=mysecurepassword
    env_file:
      - ./mysql_conf.env // <---
    // replaces
    // MYSQL_PASSWORD=myothersecurepassword
    // MYSQL_DATABASE=nextcloud
    // MYSQL_USER=nextcloud

  letsencrypt-companion:
    image: jrcs/letsencrypt-nginx-proxy-companion
    container_name: nextcloud-letsencrypt
    restart: unless-stopped
    networks:
      - nextcloud-network
    volumes:
      - ./proxy/certs:/etc/nginx/certs:rw
      - ./proxy/vhost.d:/etc/nginx/vhost.d:rw
      - ./proxy/html:/usr/share/nginx/html:rw
      - /etc/localtime:/etc/localtime:ro
      - /var/run/docker.sock:/var/run/docker.sock:ro
    depends_on:
      - proxy

  app:
    image: nextcloud:latest
    container_name: nextcloud-app
    restart: unless-stopped
    networks:
      - nextcloud-network
    volumes:
      - ./app/config:/var/www/html/config
      - ./app/custom_apps:/var/www/html/custom_apps
      - ./app/themes:/var/www/html/themes
      - ./app/core/skeleton:/var/www/html/core/skeleton
      - nextcloud-html:/var/www/html
      - nextcloud-data:/var/www/html/data
    environment:
      - MYSQL_HOST=db // <--- prefills your first login site where you have to bind to your db
      - VIRTUAL_HOST=myurl.org
      - LETSENCRYPT_HOST=myurl.org
      - LETSENCRYPT_EMAIL=my@mail.de
    env_file:
      - ./mysql_conf.env // <--- prefills your first login site where you have to bind to your db

volumes:
  nextcloud-html:
    name: nextcloud-html
    driver: local-persist
    driver_opts:
      mountpoint: /<pathToMainFolder>/html
  nextcloud-data:
    name: nextcloud-data
    driver: local-persist
    driver_opts:
      mountpoint: /<pathToMainFolder>/data
  db:
    name: nextcloud-db
    driver: local-persist // <--- for not loosing the db again
    driver_opts:          // <--- for not loosing the db again
      mountpoint: /<pathToMainFolder>/db // <--- for not loosing the db again

networks:
  nextcloud-network:
    name: nextcloud-network

The part of .htaccess in /var/www/html/ or the bound path on my machine /pathToMainFolder/html/

#### DO NOT CHANGE ANYTHING ABOVE THIS LINE ####

ErrorDocument 403 //
ErrorDocument 404 //
<IfModule mod_rewrite.c>
  Options -MultiViews
  RewriteRule ^core/js/oc.js$ index.php [PT,E=PATH_INFO:$1]
  RewriteRule ^core/preview.png$ index.php [PT,E=PATH_INFO:$1]
  RewriteCond %{REQUEST_FILENAME} !\.(css|js|svg|gif|png|html|ttf|woff2?|ico|jpg|jpeg|map|webm|mp4|mp3|ogg|wav)$
  // bla
  // bla
  // bla
  RewriteRule . index.php [PT,E=PATH_INFO:$1]
  RewriteBase /cloud // <--------------- Important.  Replace with your subpath
  <IfModule mod_env.c>
    SetEnv front_controller_active true
    <IfModule mod_dir.c>
      DirectorySlash off
    </IfModule>
  </IfModule>
</IfModule>

The part of my config.php in /var/www/html/config/ or the bound path on my machine /pathToMainFolder/app/config/

  // Proxy
  'overwriteprotocol' => 'https',
  'overwritehost' => 'myurl.org',
  'overwritewebroot' => '/cloud', // <--- Important.  Replace with your subpath
  'overwritecondaddr' => '',
  'htaccess.RewriteBase' => '/',

I hope i helped someone with similar problems.