<?php wp_reset_postdata(); ?>
↓
<?php $loop->reset_postdata(); ?>
<?php $loop = new WP_Query($args); ?>
<?php if ( $loop->have_posts() ) : while ( $loop->have_posts() ) : $loop->the_post(); ?>
<?php
// HERE STARTS THE POST OBJECT PART TO SHOW DATA FROM THE LINKED POST
$post_object = get_field('kurs_zu_diesem_seminar');
if( $post_object ):
// override $post
$post = $post_object;
setup_postdata( $post );
?>
<h3><a>"><?php the_title(); ?></a></h3>
<?php $loop->reset_postdata(); ?>
<?php endif; ?>
// END POST OBJECT PART
// START SHOW DATA FROM DEFAULT OBJECT
<span class="title"><?php the_title(); ?> am <?php the_field('start_datum'); ?></span>
<?php the_field('beschrieb'); ?>
<?php endwhile; ?>
<?php else: ?>
<p>Aktuell sind keine Seminare geplant.</p>
<?php endif; ?>
<?php wp_reset_postdata(); ?>
