Get args from URL in Drupal 8

Example: 

    $current_url = Url::fromRoute('<current>');

    $path = $current_url->toString();

    //OR of you want to get the url without language prefix

    $path = $current_url->getInternalPath();

    $path_args = explode('/', $path);

Method 2: (Get first argument from url on Drupal 8)

$request = \Drupal::request();

$current_path = $request->getPathInfo();

$path_args = explode('/', $current_path);

$first_argument = $path_args[1];