WordPress sorting filter brings me back to the homepage

I´m making a WordPress website and I want to have a filter on mine search.php file. But whenever I select an option, he brings me back to my homepage instead of being on the same file. I think it has something to do with my url. On the page with the filter, I already have a ?s= in my url. I don’t know how I can fix this in my code that my url has after the ?s= also /?sort=. I don’t if this is even possible, I’m still new to coding.
This is my code (sorry for the ducth words 😉 )

<form method="get" action="<?php echo esc_url(home_url('/')); ?>" class="sortering-form">
   <label for="sortering">Sorteer op:</label>
   <select name="sort" id="sortering" onchange="this.form.submit()">
      <option value="nieuw" <?php selected($_GET['sort'] ?? '', 'nieuw'); ?>>Nieuw → Oud</option>
      <option value="oud" <?php selected($_GET['sort'] ?? '', 'oud'); ?>>Oud → Nieuw</option>
      <option value="titel" <?php selected($_GET['sort'] ?? '', 'titel'); ?>>Titel A → Z</option>
      <option value="random" <?php selected($_GET['sort'] ?? '', 'random'); ?>>Willekeurig</option>
   </select>
</form>