tracking code to heureka page

-- HikaShop version -- : 4.2.2
-- Joomla version -- : 3.9.8
-- PHP version -- : 7.2.7
-- Browser(s) name and version -- : chrome

Hello,

can You please help me with implementing tracking code to hikashop?
As I find out, it should go in view end.php
code should look like:

<?php
require_once __DIR__ . '/../vendor/autoload.php';
try {
// Use your own API key here. And keep it secret!
$apiKey = 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx';
$options = [
// Use \Heureka\ShopCertification::HEUREKA_SK if your e-shop is on heureka.sk
'service' => \Heureka\ShopCertification::HEUREKA_SK,
];
$shopCertification = new \Heureka\ShopCertification($apiKey, $options);
// Set customer email - it is MANDATORY.
$shopCertification->setEmail('This email address is being protected from spambots. You need JavaScript enabled to view it.');
// Set order ID - it helps you track your customers' orders in Heureka shop administration.
$shopCertification->setOrderId(1597884);

// And finally send the order to our service.
$shopCertification->logOrder();
// Everything went well - we are done here.

I need to import in this code user mail who created the order and also order number

Thank You for Your replay
I implemented it like this:

<?php
require_once __DIR__ . '/../vendor/autoload.php';
try {
// Use your own API key here. And keep it secret!
$apiKey = 'xxxxxxxxxxxxxxxxxxxxxxxxxxxx';
$options = [
// Use \Heureka\ShopCertification::HEUREKA_SK if your e-shop is on heureka.sk
'service' => \Heureka\ShopCertification::HEUREKA_SK,
];
$shopCertification = new \Heureka\ShopCertification($apiKey, $options);
// Set customer email - it is MANDATORY.
$shopCertification->setEmail('$this->order->customer->user_email');
// Set order ID - it helps you track your customers' orders in Heureka shop administration.
$shopCertification->setOrderId($this->order->order_id);

// And finally send the order to our service.
$shopCertification->logOrder();
// Everything went well - we are done here.


but get this error:
Warning: require_once(/www/e/n/u123817/public_html/libraries/joomla/document/html/renderer/head.php): failed to open stream: No such file or directory in /www/e/n/u123817/public_html/templates/sj_thecool_free/error.php on line 44

Fatal error: require_once(): Failed opening required '/www/e/n/u123817/public_html/libraries/joomla/document/html/renderer/head.php' (include_path='.:/usr/local/php72/lib/php') in /www/e/n/u123817/public_html/templates/sj_thecool_free/error.php on line 44

I am not programmer and dont know what is wrong

I would be gratefull if You can help me

thank You