Hi.

Please use next css in child theme

function thegem_child_init() {
    remove_action('thegem_woocommerce_single_product_bottom', 'thegem_woocommerce_single_product_navigation', 10);
    remove_action('thegem_woocommerce_single_product_right', 'thegem_woocommerce_back_to_shop_button', 5);
}
add_action('init', 'thegem_child_init');

Sorry for the error, this code needs to be added to the functions.php file of your child theme.

But you can use custom CSS:

.single-product-content-bottom .block-navigation {
    display: none !important;
}
.single-product-content .back-to-shop-button {
    display: none !important;
}