Order terms by count – missing terms

By default hide_empty is true for get_terms. So i guess you must be missing terms which do not have posts. Try this,

<?php $terms = get_terms("autorzy", array('orderby' => 'count', 'order' => 'DESC','hide_empty'=>0 ));
    $count = count($terms);
    if ( $count > 0 ){
    echo "<div>";
        foreach ( $terms as $term ) { ?>
<?php echo $term->name; ?>
<a href="https://wordpress.stackexchange.com/questions/139869/<?php get_term_link( $term ); ?>" class="avatar-link"></a>
<?php echo term_description( $term->term_id, 'autorzy' ) ?>
    <?php } echo "</div>"; } ?>