Multiple post back-to-back display only one gallery

Hourray : find it : do_shortcode do the trick !

here is the final code :

// --------------------------------------------------------------------------------------------------------------------
//Add a ShorCode to get a page/post content
add_shortcode ('post_cat3','get_post_cat3');
   function get_post_cat3 ($att) {

       $query = new WP_Query( 'cat=36' );
       if ($query->have_posts()) : while ($query->have_posts()) : $query->the_post();

        $aaa .= '<p>------------</p>'.do_shortcode(get_the_content());

        endwhile; 
        endif; 
        return do_shortcode($aaa);
   }