WordPress Custom Post add new column in admin

//Additional Admin Column Experts
add_filter('manage_expert_posts_columns', 'c2_filter_posts_columns');
function c2_filter_posts_columns($columns)
{
 $columns['related_talks'] = __('Related Talks', 'experts');
 $columns['related_gifts'] = __('Related Gifts', 'experts');
 $columns['related_sponsors'] = __('Related Sponsors', 'experts');
 return $columns;
}
add_action('manage_expert_posts_custom_column', 'c2_related_info_column', 10, 2);
function c2_related_info_column($column, $post_id)
{
 // Related Talks column
 if ('related_talks' === $column) {
  get_post_column_data($post_id, 'talk');
 }
 // Related gifts column
 if ('related_gifts' === $column) {
  get_post_column_data($post_id, 'gift');
 }
 // Related sponsors column
 if ('related_sponsors' === $column) {
  get_post_column_data($post_id, 'sponsor');
 }
}
function get_post_column_data($c_post_id, $post_type)
{
 $num_count = 0;
 $ass_ex = array(
  'post_type'  => $post_type,
  'separater'  => ', ',
  'meta_query' => array(
   array(
    'key'   => '_cb_gifts',
    'value' => $c_post_id,
    'compare' => 'LIKE',
   )
  )
 );
 $queryex = new WP_Query($ass_ex);
 $num_of_items = $queryex->found_posts;;
 if ($queryex->have_posts()) {
  while ($queryex->have_posts()) {
   $queryex->the_post(); ?>
   <a href="<?php echo get_edit_post_link(get_the_ID()); ?>">
    <?php the_title(); ?>
   </a>
   <?php
   $num_count = $num_count + 1;
   if ($num_count < $num_of_items) {
    echo ", ";
   }
  }
  wp_reset_postdata();
 } else {
  _e('—');
 }
}