WooCommerce link to related product on a specific thing

I want to add a link to related product on the a with 'Obtenir en Grade Pro'. All my product have only 1 related element.

I am not able to have ONLY the link to the related product.

I am able to have the image, title and couple of thing of the related product but I can't have ONLY the link. How can I do that?

<?php
/**
 * The main template file.
 *
 * This is the most generic template file in a WordPress theme
 * and one of the two required files for a theme (the other being style.css).
 * It is used to display a page when nothing more specific matches a query.
 * E.g., it puts together the home page when no home.php file exists.
 * Learn more: http://ift.tt/vTku09
 *
 * @package storefront
 */
get_header();
 ?> 

    <div id="primary" class="content-area">
        <main id="main" class="site-main" role="main">
        <?php if( is_home() ) : ?>
            <section id="recent">

    <h2>Les différents bâtons</h2>

    <?php
     $args = array( 'post_type' => 'product', 'meta_key' => '_featured','posts_per_page' => 15,'columns' => '3', 'meta_value' => 'yes' );
     $loop = new WP_Query( $args );?>
     <ul class="products">
     <?php while ( $loop->have_posts() ) : $loop->the_post(); global $product; ?>
        <li class="product">
            <?php if (has_post_thumbnail( $loop->post->ID )) echo get_the_post_thumbnail($loop->post->ID, 'shop_catalog'); else echo '<img src="'.woocommerce_placeholder_img_src().'" alt="Placeholder" width="300px" height="300px" />'; ?>
            <h3><?php the_title(); ?></h3>
            <span class="price"><?php echo $product->get_price_html(); ?></span>
            <a>" title="<?php the_title(); ?>">
            <div class="hover-fiche"><p>Fiche complète du produit</p></div>
        </a>

//ADD THE LINK TO RELATED PRODUCT IN THE A
    <a href="LINK TO RELATED PRODUCT HERE">
    <div class="gradeprobutton">Obtenir en Grade Pro</div>
    <img src="wp-content/themes/storefront-child/images/info.png" alt="informations supplémentaires">
    <span class="gradepro">
        Bois de gamme *grade pro* sélectionné et confectionné dans un de nos 4 modèles. Il est seulement disponible dans notre édition spéciale pour la couleur.(99.99$)
    </span>
</a>

<!--Second tooltip-->
<!--<div class="gradeprodiv">
                     <a>post->ID ); ?>"><span class="gradeprobutton">Obtenir en grade Pro</span> <span class="info-icon"><div class="info"><p>Bois de gamme *grade pro* sélectionné et confectionné dans un de nos 4 modèles. Il est seulement disponible dans notre édition spécial pour la couleur </p></div></span></a>
</div> -->

                <?php
            /**
             * woocommerce_pagination hook
             *
             * @hooked woocommerce_pagination - 10
             * @hooked woocommerce_catalog_ordering - 20
             */
            do_action( 'woocommerce_pagination' );
        ?>
<?php endwhile; ?>

<?php wp_reset_query(); ?>

        <?php wp_reset_query(); ?>

</section><!-- /recent -->
        <?php else : ?>

            <?php get_template_part( 'content', 'none' ); ?>

        <?php endif; ?>

        </main><!-- #main -->
    </div><!-- #primary -->
<?php get_footer(); ?>

Thank you for everyone who will give a answer.

via Chebli Mohamed