Custom post types archive

I'm developing my first custom theme from scratch (using Roots as base framework). The theme has 2 CPT, one for events and one for associations with a correlation one to many between the two (an association can have many events associated).

I modified the main query with pre_get_posts to display events in homepage.

Now I want to create a widget on sidebar to display a list of the associations that have events associated with them. I also want to display the number of events associated near the name of every association. If I click on one of them, I want to go on an archive page with a list events only for that association.

Think of it like the standard archive plugin but with associations instead of months.

I don't have idea of which type of query I have to do inside the custom widget main function. This is my code at the moment:

private function getAssociationsList(){

  // The Query
  $associations = new WP_Query( array('post_type' => 'associations' ) );

  if($associations->found_posts > 0) {
    echo '<ul>';
      while ($associations->have_posts()) {
        $associations->the_post();

        $events_query = array(
          'post_type' => 'events',
          'meta_query'=> array(
            array(
              'key'   => 'mlw_event_association',
              'value' => get_the_ID()
            )
          )
        );

        $events_for_this_association = new WP_Query($events_query);

        if($events_for_this_association->found_posts > 0){
          $listItem = '<li>'; 
          $listItem .= '<a href="' . get_permalink() . '">';
          $listItem .= get_the_title() . '</a>';
          $listItem .= ' ('. $events_for_this_association->post_count . ')</li>'; 
          echo $listItem;
        }
      }
    echo '</ul>';
    wp_reset_postdata(); 

  }else{
    echo '<p>_("No association with upcoming events at the moment")</p>';
  } 
}

The problem here is that get_permalink() is the link to the association page, not to a "filtered" archive page. Also with this query the tag is always shown, even if there aren't associations with events associated.

Any suggestion would be very appreciated.

Thank you!