Render Url::fromUri + Language (Drupal)

Use:

use Drupal\Core\Controller\ControllerBase;
use Drupal\Core\Database\Database;
use Drupal\Core\Link;
use Drupal\Core\Url;
use Drupal\Core\Language\Language;

Language Manager:

    $languageManager = \Drupal::service('language_manager');
    $language_de = $languageManager->getLanguage('de');

URL / Link as HTML:

    $url_string = "my-content-url-123";
    $url = Url::fromUri('internal:'.$url_string, ['language' => $language_de] );
    $link = Link::fromTextAndUrl($label, $url);
    $link = $link->toRenderable();
    $link['#attributes'] = ['class' => ['internal']];
    $html = \Drupal::service('renderer')->render( $link );