$first = new WP_Query('post_type=success-stories&posts_per_page=1&order=DESC'); $first->the_post();

<?php $prevPost = get_previous_post(); ?>
<?php if($prevPost) {
    $args = array(
        'post_type'         => 'success-stories',
        'posts_per_page'    => 1,
        'include'           => $prevPost->ID
    );
    $prevPost = get_posts($args);
    foreach ($prevPost as $post) {
        setup_postdata($post); ?>

            <div class="hide-medium blogpost-link">
                <a href="<?php the_permalink(); ?>"></a>
                <?php $thumbnail = get_field('sv_thumbnail_image'); ?>
                <div class="bg-image" style="background-image: url(<?php echo $thumbnail['url']; ?>)"></div>
                <div class="overlay">
                    <div class="inner">
                        <div class="icon">
                            <?php
                                $client_image = get_field('blog_client_logo');
                                if( ! empty($client_image) ):
                                    echo '<img src="' . $client_image['url'] . '" alt="">';
                                endif;
                            ?>
                        </div>
                        <div class="vertical-centered text-center text">
                            <h3> <?php the_title(); ?> </h3>
                            <a class="btn inline-block solid-btn" href="<?php the_permalink(); ?>">Lees verder</a>
                        </div>
                    </div>
                </div>
            </div>
            <div class="show-medium small-6 prev previous-link">
                <a href="<?php the_permalink(); ?>">&larr; Vorige</a>
            </div>

        <?php wp_reset_postdata();
    } //end foreach
} else {
    $first = new WP_Query('post_type=success-stories&posts_per_page=1&order=DESC'); $first->the_post(); ?>

        <div class="hide-large blogpost-link">
            <a href="<?php the_permalink(); ?>"></a>
            <?php $thumbnail = get_field('sv_thumbnail_image'); ?>
            <div class="bg-image" style="background-image: url(<?php echo $thumbnail['url']; ?>)"></div>
            <div class="overlay">
                <div class="inner">
                    <div class="icon">
                        <?php
                            $client_image = get_field('blog_client_logo');
                            if( ! empty($client_image) ):
                                echo '<img src="' . $client_image['url'] . '" alt="">';
                            endif;
                        ?>
                    </div>
                    <div class="vertical-centered text-center text">
                        <h3> <?php the_title(); ?> </h3>
                        <a class="btn inline-block solid-btn" href="<?php the_permalink(); ?>">Lees verder</a>
                    </div>
                </div>
            </div>
        </div>
        <div class="show-medium  small-6 prev previous-link">
            <a href="<?php the_permalink(); ?>">&larr; Vorige</a>
        </div>

    <?php   wp_reset_query();
} ?>