Drupal 8.x

I am new to module development, I have developed a custom module to create node programatically and dynamically. I got stuck when adding multiple files/images in field. I am using this code found from the community answer & worked for me.

Hello,

I'm about to start a new site, it would be my first Drupal 8 (have build several Drupal 7 sites).

Most of the content of this new project comes from an external xml file. The site would be syncing every hour with the xml file: adding, updating and deleting nodes depending on the xml source. So I heavily depend on this process.

Looks I have two options:

I have set up Apache2 site (currently local dev) with Drupal 8 multisite, following this guide: https://www.drupal.org/docs/8/multisite/drupal-8-multisite

The system where all this is running is in a Docker container, based on Ubuntu.

The Drupal was installed by root user, and the associated Apache site user is www-data.

My dev Drupal stopped working by showing the following message:

The website encountered an unexpected error. Please try again later.

I have assumed that it is something to do with php extensions or making the subtheme of bootstrap_barrio.

Also some messages appeared suggesting that some php extensions are not installed even thought I have reinstalled many of them and restarting the server.

As it was quite new website reinstallation was done using Composer.

However now I can not go past through installation as the following message appears: