Owncloud on docker behind apache revers proxy OWNCLOUD_SUB_URL not working

Can someone please help me?
I actually have two problems with docker compose. I use Debian on a virtual machine (IP: 192.168.1.13). An Apache container acts as a relay host. (Container IP: 172.16.0.1).
Here is my docker-compose.yml:

version: "2"  

volumes:
  files:
    driver: local
  mysql:
    driver: local
  backup:
    driver: local
  redis:
    driver: local

services:
  owncloud:
    image: owncloud/server:${OWNCLOUD_VERSION}
    container_name: owncloud   
    restart: always
    ports:
      - ${HTTP_PORT}:8080
    depends_on:
      - ownclouddb
    environment:
      - OWNCLOUD_DOMAIN=${OWNCLOUD_DOMAIN}
      - OWNCLOUD_TRUSTED_DOMAINS=${OWNCLOUD_TRUSTED_DOMAINS}
      #Database
      - OWNCLOUD_DB_TYPE=mysql
      - OWNCLOUD_DB_NAME=owncloud
      - OWNCLOUD_DB_USERNAME=owncloud
      - OWNCLOUD_DB_PASSWORD=${ADMIN_PASSWORD}
      - OWNCLOUD_DB_HOST=ownclouddb
      #Owncloud
      - OWNCLOUD_ADMIN_USERNAME=${ADMIN_USERNAME}
      - OWNCLOUD_ADMIN_PASSWORD=${ADMIN_PASSWORD}
      - OWNCLOUD_MYSQL_UTF8MB4=true
      #Relay Proxy 
      - OWNCLOUD_OVERWRITE_CLI_URL=https://192.168.1.13/owncloud #Problem No. 1
      - OWNCLOUD_OVERWRITE_PROTOCOL=https
      - OWNCLOUD_OVERWRITE_HOST=192.168.1.13/owncloud 
      - OWNCLOUD_TRUSTED_PROXIES=192.168.1.13, 172.16.0.1
      - OWNCLOUD_SUB_URL = /owncloud
      #Container
      - ImageName = owncloud.server 
    healthcheck:
      test: ["CMD", "/usr/bin/healthcheck"]
      interval: 30s
      timeout: 10s
      retries: 5
    volumes:
      - /opt/docker/owncloud/volumes/server/data:/mnt/data #Problem No. 2
    networks: 
      net:
        ipv4_address: 172.16.0.8       

  ownclouddb:
    image: mariadb:10.11
    container_name: ownclouddb
    restart: always
    environment:
      - MYSQL_DATABASE=owncloud
      - MYSQL_USER=owncloud
      - MYSQL_PASSWORD=${ADMIN_PASSWORD}          
      - MYSQL_ROOT_PASSWORD=${RootPW} 
      - MYSQL_MAX_ALLOWED_PACKET=128M
      - MYSQL_INNODB_LOG_FILE_SIZE=64M       
      - ImageName = owncloud.mariadb 
      - MARIADB_AUTO_UPGRADE=1 
    networks: 
      net:
        ipv4_address: 172.16.0.9         
          
networks:                              
  net:                   
    external:                
      name: apache_net

Problem No 1:
The entries for the proxy relay (see section ‘#Relay Proxy’) do not appear in config.php. What could be the reason for this?

Problem No 2:

I map a directory of the host to be able to check the config.php after creating the container (see “volumes” of server). When I set this up and create the container, everything works at fine. But after a “docker compose down” and “docker compose up -d” the owncloud container crashes with the following error message:

SQLSTATE[42S02]: Base table or view not found: 1146 Table 'owncloud.oc_appconfig' doesn't exist in /var/www/owncloud/lib/composer/doctrine/dbal/lib/Doctrine/DBAL/Driver/AbstractMySQLDriver.php:53
Stack trace:
#0 /var/www/owncloud/lib/composer/doctrine/dbal/lib/Doctrine/DBAL/DBALException.php(128): Doctrine\DBAL\Driver\AbstractMySQLDriver->convertException('An exception oc...', Object(Doctrine\DBAL\Driver\PD
OException))
#1 /var/www/owncloud/lib/composer/doctrine/dbal/lib/Doctrine/DBAL/Connection.php(855): Doctrine\DBAL\DBALException::driverExceptionDuringQuery(Object(Doctrine\DBAL\Driver\PDOMySql\Driver), Object(Doctr

That’s why I have to delete the images afterwards and reinstall them. Without an ‘volumes’ entry it works fine. What can I do to avoid this?

Many thanks for any help

Stefan