Is it possible to give to a specific user role the permission to create content only in a language?
Create a custom module for this. I'm including some code that may help get you started. The idea behind this code (below) is preventing a user without the role 'admin_de' from editing content that has a different language than what the 'admin_de' user has set for their account. So there are some obvious differences, but this should be a good start.

In MY_MODULE.info.yml:

name: MY_MODULE
type: module
description: Allows user with particular role to edit content of particular 
language.
core: 8.x


In a file called MY_MODULE.permissions.yml, include:

edit same language:
  title: 'Edit Same Language Only'
  description: 'Allow user to edit only nodes matching their account language'


In a file called MY_MODULE.module, include:

&lt;?php

use \Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Entity\EntityForm;

/**
 * Implements hook_form_alter().
 */
function MY_MODULE_form_alter(&amp;$form, FormStateInterface $form_state, $form_id) {
  $currentUser = Drupal::currentUser();
  $roles = $currentUser-&gt;getRoles();

  if (in_array('admin_de', $roles)) {
    switch ($form_id) {
      case 'node_CONTENT_TYPE_edit_form':
        $currentUserLanguages = getUserLanguage($currentUser-&gt;id());
        $submissionLanguage = getSubmissionLanguage($form_state);
        $status = (Drupal::currentUser()
        -&gt;hasPermission('edit same language') &amp;&amp; ($submissionLanguage == $currentUserLanguages));
        if (!$status) {
          throw new \Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException();
        }
        break;
    }
  }
}

/**
 * @param $userId
 * logged in user id
 *
 * @return string of language id logged in user is associated with.
 */
function getUserLanguage($userId) {
  $user = \Drupal\user\Entity\User::load($userId);
  $languageId = $user-&gt;language()-&gt;getId();

  return $languageId;
}

/**
 * @param FormStateInterface $form_state
 *
 * @return string language id of page
 */
function getSubmissionLanguage(FormStateInterface $form_state) {
  $language = '';
  $form_object = $form_state-&gt;getFormObject();
  if ($form_object instanceof EntityForm) {
    $entity = $form_object-&gt;getEntity();
    $language = $entity-&gt;langcode-&gt;value;
  }

  return $language;
}


Hope this helps!