Choosing and installing multilingual modules
How to use setup the multilingual capability of your Drupal 8 site.
Translating content
How to start translating content on your Drupal site.
Translating site interfaces
How to setup a multilingual built-in user interface of your Drupal 8 site.
Install a language
Install a new language on your Drupal 8 site.
Enable language detection
Enabling and setup of the language detection.
Translating configuration
How to translate configuration in Drupal 8+ using built-in translation module.
Adding a language to Drupal core
A tutorial on how to add a language to Drupal: gather key information, create a team at localize.drupal.org, modify core itself.
Setting the language for administration pages
This page describes how to set the language of the administration pages.