Drupal 8.x

I need a developer to design a classified ads website that supports Arabic language and periodic update work.

I've got an issue every time I create/save new nodes or blocks I've got this message:

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

In the Recent log messages, I can see the following message:

InvalidArgumentException: Class "Drupal\content_moderation\Plugin\Validation\Constraint\ModerationStateConstraintValidator" does not exist. in Drupal\Core\DependencyInjection\ClassResolver->getInstanceFromDefinition() (line 24 of /website.com/core/lib/Drupal/Core/DependencyInjection/ClassResolver.php).

Hello,

I'm new in drupal 8 world and I'm trying to make my first steps in theming.

Because I want to use different libraries to different pages I realized that I cannot attach libraries If I use hook_name_suggestions.

In my node.html.twig I'm attaching a library as normal:

{{ attach_library('anitas/node_styles') }}

but If I use hook_name_suggestions like html--node--1.html.twig

and in the new content insert

{{ attach_library('anitas/node_1_styles') }}

I recently learned, with the help of this forum, how to upgrade my vendor and core files using Composer. It's starting to click more each time I use it, but there was certainly a steep learning curve.

I ran $ composer outdated and found the following:

I love the VOIP module.

https://www.drupal.org/project/voipdrupal

but it does not look like it will ever have a Drupal 8 module. I dont see a single VOIP mod for drupal 8.

I really want to focus on Drupal 8. 

How do I learn to make VOIP features into Drupal 8? 

Any advice greatly appreciated. 

I have a custom Drupal (8) theme I have been putting together from scratch, and 2 CentOS web servers built to be as identical as possible.

Part way finished, I copied the theme I was working on in DEV onto PROD so the stakeholder could look at its progress.  It worked alright, though it was not finished.

I continued to build the theme on the DEV box and am trying to apply it to the PROD server.