Create a new version of paste:

<?php
// get next and prev products

function ShowLinkToProduct($post_id, $categories_as_array, $label) {
    // get post according post id
    $query_args = array( 'post__in' => array($post_id), 'posts_per_page' => 1, 'post_status' => 'publish', 'post_type' => 'product', 'tax_query' => array(
        array(
            'taxonomy' => 'product_cat',
            'field' => 'id',
            'terms' => $categories_as_array
        )));
    $r_single = new WP_Query($query_args);
    if ($r_single->have_posts()) {
        $r_single->the_post();
        global $product;
    ?>
    <li style="display: inline-block !important; margin-right: 300px;">
        <a href="<?php the_permalink() ?>" title="<?php echo esc_attr(get_the_title() ? get_the_title() : get_the_ID()); ?>">
            <?php if (has_post_thumbnail()) the_post_thumbnail('shop_thumbnail'); else echo '<img src="'. woocommerce_placeholder_img_src() .'" alt="Placeholder" width="'.$woocommerce->get_image_size('shop_thumbnail_image_width').'" height="'.$woocommerce->get_image_size('shop_thumbnail_image_height').'" />'; ?>
            <?php echo $label; ?>
            <?php if ( get_the_title() ) the_title(); else the_ID(); ?>
            <?php echo $product->get_price_html(); ?>
        </a>
    </li>
    <?php
        wp_reset_query();
    }
}

if ( is_singular('product') ) {
    global $post;

    // get categories
    $terms = wp_get_post_terms( $post->ID, 'product_cat' );
    foreach ( $terms as $term ) $cats_array[] = $term->term_id;

    // get all posts in current categories
    $query_args = array('posts_per_page' => -1, 'post_status' => 'publish', 'post_type' => 'product', 'tax_query' => array(
        array(
            'taxonomy' => 'product_cat',
            'field' => 'id',
            'terms' => $cats_array
        )));
    $r = new WP_Query($query_args);

    // show next and prev only if we have 3 or more
    if ($r->post_count > 2) {

        $prev_product_id = -1;
        $next_product_id = -1;

        $found_product = false;
        $i = 0;

        $current_product_index = $i;
        $current_product_id = get_the_ID();

        if ($r->have_posts()) {
            while ($r->have_posts()) {
                $r->the_post();
                $current_id = get_the_ID();

                if ($current_id == $current_product_id) {
                    $found_product = true;
                    $current_product_index = $i;
                }

                $is_first = ($current_product_index == $first_product_index);

                if ($is_first) {
                    $prev_product_id = get_the_ID(); // if product is first then 'prev' = last product
                } else {
                    if (!$found_product && $current_id != $current_product_id) {
                        $prev_product_id = get_the_ID();
                    }
                }

                if ($i == 0) { // if product is last then 'next' = first product
                    $next_product_id = get_the_ID();
                }

                if ($found_product && $i == $current_product_index + 1) {
                    $next_product_id = get_the_ID();
                }

                $i++;
            }

            echo '<ul class="product_list_widget">';
			if ($next_product_id != -1) { ShowLinkToProduct($next_product_id, $cats_array, "Prev:<br> "); }
			
            if ($prev_product_id != -1) { ShowLinkToProduct($prev_product_id, $cats_array, "Next:<br> "); }
            
            echo '</ul><hr>';
        }

        wp_reset_query();
    }
}
?>


<?php
/**
 * The template for displaying product content in the single-product.php template
 *
 * This template can be overridden by copying it to yourtheme/woocommerce/content-single-product.php.
 *
 * HOWEVER, on occasion WooCommerce will need to update template files and you
 * (the theme developer) will need to copy the new files to your theme to
 * maintain compatibility. We try to do this as little as possible, but it does
 * happen. When this occurs the version of the template file will be bumped and
 * the readme will list any important changes.
 *
 * @see     https://woo.com/document/template-structure/
 * @package WooCommerce\Templates
 * @version 3.6.0
 */

defined( 'ABSPATH' ) || exit;

global $product;

/**
 * Hook: woocommerce_before_single_product.
 *
 * @hooked woocommerce_output_all_notices - 10
 */
do_action( 'woocommerce_before_single_product' );

if ( post_password_required() ) {
	echo get_the_password_form(); // WPCS: XSS ok.
	return;
}
?>
<div id="product-<?php the_ID(); ?>" <?php wc_product_class( '', $product ); ?>>

	<?php
	/**
	 * Hook: woocommerce_before_single_product_summary.
	 *
	 * @hooked woocommerce_show_product_sale_flash - 10
	 * @hooked woocommerce_show_product_images - 20
	 */
	do_action( 'woocommerce_before_single_product_summary' );
	?>

	<div class="summary entry-summary">
		<?php
		/**
		 * Hook: woocommerce_single_product_summary.
		 *
		 * @hooked woocommerce_template_single_title - 5
		 * @hooked woocommerce_template_single_rating - 10
		 * @hooked woocommerce_template_single_price - 10
		 * @hooked woocommerce_template_single_excerpt - 20
		 * @hooked woocommerce_template_single_add_to_cart - 30
		 * @hooked woocommerce_template_single_meta - 40
		 * @hooked woocommerce_template_single_sharing - 50
		 * @hooked WC_Structured_Data::generate_product_data() - 60
		 */
		do_action( 'woocommerce_single_product_summary' );
		?>
	</div>

	<?php
	/**
	 * Hook: woocommerce_after_single_product_summary.
	 *
	 * @hooked woocommerce_output_product_data_tabs - 10
	 * @hooked woocommerce_upsell_display - 15
	 * @hooked woocommerce_output_related_products - 20
	 */
	do_action( 'woocommerce_after_single_product_summary' );
	?>
</div>

<?php do_action( 'woocommerce_after_single_product' ); ?>