Drupal - How do I get parameters from form redirect?

Ok i got it by this way :

So i have 2 parameters from my form to pass to my controller :

public function submitForm(array &$form, FormStateInterface $form_state)
{

    $metier=$form_state->getValue('metier');
    $position=$form_state->getValue('position');

    $url = \Drupal\Core\Url::fromRoute('recherche.resultat')
          ->setRouteParameters(array('metier'=>$metier,'position'=>$position));

    $form_state->setRedirectUrl($url);


}

The key is in the YAML routing, you need to build your path like that for get parameters ( name of parameters need to be same as your route, see previous function (submitForm)) :

recherche.resultat:
  path: '/resultat/{metier}/{position}'
  defaults:
    _title: 'resultat'
    _controller: '\Drupal\recherche\Controller\ResultatRechercheController::resultat'
    metier: ''
    position: ''
  requirements:
     _permission: 'access content'

And in my controller for get my parameters :

Class: ResultatRechercheController

 public function resultat($metier, $position)
    {

        kint($metier);
        kint($position);

        return array('#markup'=>t('la premiere spécialite est @specialite',array('@specialite'=>'test')));

    }

And the URL is clean :

localhost:8888//monsite.com/resultat/{metier}/{position}

You can get the get attributes directly from the request object \Drupal::request()->attributes->get('param'); or \Drupal::request()->query

Source: https://api.drupal.org/api/drupal/core%21lib%21Drupal.php/function/Drupal%3A%3Arequest/8