Refer to 3 items on a template

Hi,
In my template, I use the item "Order". I need to access the "Product" item, contained in the "Order". I found this code on another topic :

add_filter('e2pdf_model_shortcode_e2pdf_wp_response', 'e2pdf_model_shortcode_e2pdf_wp_response_key2', 10, 3);

function e2pdf_model_shortcode_e2pdf_wp_response_key2($response, $atts, $value) {

if (isset($atts['key2']) && $atts['key2']) {
$post_meta = false;
if ($response) {
$post_meta = get_post_meta($response, $atts['key2'], true);
}
if ($post_meta !== false) {
$response = $post_meta;
} else {
$response = '';
}
}
return $response;
}

it works, but now I also need to acces the item "Course", which is the first object contained in the array "Courses" in the product. Could you help me with the code that I need to add "key3" and "path2" in the shortcodes please ?