posts_nav_link not working

<?php
$geen_jeugd = new WP_Query('cat=-5&posts_per_page=6');
while ($geen_jeugd->have_posts()) : $geen_jeugd->the_post();
?>
<div class="nieuwsbericht clearfix">
<div class="thumb">
<?php
if(has_post_thumbnail()) {
	the_post_thumbnail();
}
else {
	echo '<img src="https://svwevelgemcity.be/wp-content/uploads/2012/06/def-thumb.png" alt="'.get_the_title().'" />';
}
?>
</div>
<div class="inhoud">
<h3><a href="<?php the_permalink(); ?>" title="<?php the_title(); ?>"><?php the_title(); ?></a></h3>
<p class="klein"><?php the_time('d/n/Y'); ?> | Categorie: <?php the_category(' &middot; '); ?></p>
<?php the_content(' '); ?>
<a href="<?php the_permalink(); ?>" title="<?php the_title(); ?>">Lees verder &raquo; </a>
</div>
<hr />
</div><!-- einde nieuwsbericht -->
<?php endwhile; ?>

<div class="span7 pager">
<p><?php posts_nav_link(' - ','&laquo; Vorige','Volgende pagina &raquo;'); ?></p>
</div><!-- einde pager -->

</div><!-- einde nieuws -->

There is something not working with the posts_nav_link. it does not show older posts when clicking it…

link to website: https://svwevelgemcity.be/nieuws