Routing issues with multi language

Have a look at this post: Routes pattern for multilanguage site

So your first route (e.g. the first one, should start like this:

'pattern' => '(?:(^[A-Za-z]{2})//?)?articles/(:any)/amp',
'action'  => function($lang, $article) {
    $lang = $lang ?: 'en'; // the default language
    // do stuff
  }