Group and list posts by custom taxonomy
I'm trying to list posts from a CPT named exposition and group them based on a custom taxonomy called date-exposition (which are meant to be years such as 2010, 2015, 2017,...) in the following form :
2019
- post 1
 - post 2
 
2018
- post 3
 - post 4
 
etc...
Closest code I managed to compile is this (it only shows one date/taxonomy-value and not the posts...) :
?php
    // Get current Category
    $get_current_cat = get_term_by('name', single_cat_title('',false), 'category');
    $current_cat = $get_current_cat-term_id;
    // List posts by the terms for a custom taxonomy of any post type
    $post_type = 'exposition';
    $tax = 'date-exposition';
    $tax_terms = get_terms( $tax, 'orderby=nameorder=ASC');
    if ($tax_terms) {
        foreach ($tax_terms  as $tax_term) {
            $args = array(
                'post_type'         = $post_type,
                $tax              = $tax_term-slug,
                'post_status'       = 'publish',
                'posts_per_page'    = -1,
                'category__in'      = $current_cat // Only posts in current category (category.php)
            );
            $my_query = null;
            $my_query = new WP_Query($args);
            if( $my_query-have_posts() ) : ?
                h2?php echo $tax_term-name; // Group name (taxonomy) ?/h2
                ?php while ( $my_query-have_posts() ) : $my_query-the_post(); ?
                    ?php $term_list = wp_get_post_terms($post-ID, 'category', array(fields = ids)); // Get post categories IDs?
                    ?php if (in_array($current_cat, $term_list) ): // Display only posts that have current category ID ?
                        h3?php the_title(); ?/h3
                    ?php endif; // if in_array ?
                ?php endwhile; // end of loop ?
            ?php endif; // if have_posts()
            wp_reset_query();
        } // end foreach #tax_terms
    } // end if tax_terms
?
Thanks for help. Please note I am really not good at PHP.