Unable to build a new container image

General
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3

Thank you @rimelek for your help!
I did manage to resolve the web app service build, while searching on internet, i found that it might be caused by some corrupt images, so i removed any stale images.
Then, tried to run docker build, and it was successful. Here is the final Dockerfile:

FROM php:7.4.12-apache
ENV http_proxy="http://10.60.120.254:8080"
RUN apt clean
RUN echo "nameserver 10.55.20.5" > /etc/resolv.conf
RUN apt-get update
RUN apt-get install -y libldap2-dev
RUN docker-php-ext-install mysqli
RUN docker-php-ext-install ldap
RUN apt-get install -y libc-client-dev libkrb5-dev && rm -r /var/lib/apt/lists/*
RUN docker-php-ext-configure imap --with-kerberos --with-imap-ssl && docker-php-ext-install imap
EXPOSE 80
CMD ["/usr/sbin/apache2ctl","-DFOREGROUND"]

and the docker-compose.yml file is as follows:

version: '3.6'

services:
 db:
  container_name: db
  image:  mariadb:10.3
  restart: always
  command: --default-authentication-plugin=mysql_native_password
  env_file:
   - .env
  ports:
   - "3306:3306"
  volumes:
   - ./db_init:/docker-entrypoint-initdb.d
   - ./db_data:/var/lib/mysql

 phpmyadmin:
  container_name: admin
  depends_on:
   - db
  image: phpmyadmin/phpmyadmin
  restart: always
  ports:
   - '8080:80'
  env_file:
   - .env

 web:
  container_name: webapp
  depends_on:
   - db
  build:
   context: ./app_dockerfile
   dockerfile: Dockerfile
  image: company_webserv
  restart: always
  env_file:
   - .env
  volumes:
   - ./app:/var/www/html
  ports:
   - 809:80

For the DNS, and proxy settings, i do have the docker machine,configured for DNS and proxy services, and it works correctly, but for containers, this did not help whatever i do…
So, if you permit to give me some ideas about making it work properly, i’d be very grateful.
Thank you so much.