single.php

<?php
/**
 * The template for displaying all single posts.
 *
 * @link https://developer.wordpress.org/themes/basics/template-hierarchy/#single-post
 *
 * @package Lance
 */

get_header(); ?>

    <div id="primary" class="content-area">
        <main id="main" class="site-main" role="main">

        <?php
        while ( have_posts() ) : the_post();

        $prevPost = get_previous_post();
        $prevThumbnail = get_the_post_thumbnail( $prevPost->ID, 'project-thumb');
        $prevTitle = get_the_title($prevPost->ID);
        $nextPost = get_next_post();
        $nextThumbnail = get_the_post_thumbnail( $nextPost->ID, 'project-thumb');
        $nextTitle = get_the_title($nextPost->ID);

        get_template_part( 'template-parts/content', get_post_format() );
        ?>


        <?php endwhile; // End of the loop. ?>

        </main><!-- #main -->

    </div><!-- #primary -->
    <div class="project-nav">

        <div class="p-nav">
            <div class="p-box">
                <?php if ($prevPost) : ?>
                <h5 class="p-post">Previous:</h5>
                <?endif;?>
                <?php
                    previous_post_link( '%link', '<span class="p-button">' . $prevThumbnail . '<h4 class="p-title">' . $prevTitle . '</h4></span>' ); ?>
            </div> <!-- p-box -->
        </div> <!-- p-nav -->

            <a href="<?php echo esc_url( home_url( '/' ) ); ?>" class="b-back-to-all">
                Back To All
            </a>



        <div class="n-nav">
            <div class="n-box">
            <?php if ($nextPost) : ?>
                <h5 class="n-post">Next:</h5>
            <? endif; ?>
                <?php
                    next_post_link( '%link', '<span class="n-button">' . $nextThumbnail . '<h4 class="n-title">' .  $nextTitle . '</h4></span>' );
                ?>
            </div>
        </div>

            </div> <!-- .project-nav -->

<?php
get_sidebar();
get_footer();