WP_Query and posts_nav_link

Hi I have a custom WP Query below the loaded post which lists 4 more articles and needs to have a pagination, but I haven't found the way how to do it. Could you please check it and let me know, what is wrong?

Posts are displaying, not the pagination.

$posts_per_page = intval( get_option( 'posts_per_page' ) ) - 1;
        $paged = ( get_query_var('paged') ) ? get_query_var('paged') : 1;

        // WP_Query arguments
        $args = array (
            'post_type'              => array( 'post' ),
            'post_status'            => array( 'publish' ),
            'paged' =>  $paged,
            'posts_per_page'         => $posts_per_page,
        );
        if ( $post_type == 'post' ) {
            $args['cat'] = $post_category;
            $args['post__not_in'] = array( $post_id );
        }

        // The Query
        $query = new WP_Query( $args );

        // The Loop
        if ( $query->have_posts() ) {

            while ( $query->have_posts() ) {
                $query->the_post();

                $current_post = $query->current_post;
				$post_count = $query->found_posts;

                switch ( $current_post ) {
					case $posts_per_page -1:
						get_template_part( 'templates/archive-bottom' );
						break;
					default:
						include(locate_template('templates/archive-middle.php'));
				}

            }
        } 

        // Restore original Post Data
        wp_reset_postdata();

and my archive-middle template

<?php if ( ( $current_post == 1 && ( is_archive() || is_home() ))  || ( $current_post == 0 && ( ! is_archive() && ! is_home() )) ) : ?>
<section data-js="articlesContent" class="articleWrapper">
    <div data-js="articlesContent__article" class="otherArticles">
<?php endif; ?>

    <article class="article article--sm">
        <?php if ( has_post_thumbnail() ) {
                    the_post_thumbnail( 'mrp-small-thumbnail' );
                }
        ?>
        <a href="<?php echo get_the_permalink( ); ?>">
            <h2 class="h3"><?php the_title(); ?></h2>
        </a>
        <div class="article__labels"><?php the_category( ' ' ); ?></div>
    </article>

<?php if ( $current_post == $posts_per_page - 2 ||  $post_count == $current_post + 1) : ?>
    <?php posts_nav_link('separator','p?edchozí ?lánky','další ?lánky'); ?>
    </div>

    <?php get_template_part( 'templates/reklama-middle' ); ?>    

</section>
<?php endif; ?>