Thank you so much for helping me, I set this code up, is that okay?

gistfile1.txt

<?php
/**
 * Shopper functions and definitions
 *
 * @link https://developer.wordpress.org/themes/basics/theme-functions/
 *
 * @package Shopper
 */

/**
 * Assign the shopper version to a var
 */
$shopper_theme              = wp_get_theme( 'shopper' );
$shopper_version = $shopper_theme['Version'];

/**
 * Set the content width based on the theme's design and stylesheet.
 */
if ( ! isset( $content_width ) ) {
	
	$content_width = 980; /* pixels */
}

$shopper = (object) array(
	'version' => $shopper_version,

	/**
	 * Initialize all the things.
	 */
	'main'       => require 'inc/class-shopper.php',
	'customizer' => require 'inc/customizer/class-shopper-customizer.php',
);


require 'inc/shopper-functions.php';
require 'inc/shopper-template-hooks.php';
require 'inc/shopper-template-functions.php';

/**
 * All for WooCommerce functions
 */
if ( shopper_is_woocommerce_activated() ) {
	
	$shopper->woocommerce = require 'inc/woocommerce/class-shopper-woocommerce.php';

	require 'inc/woocommerce/shopper-wc-template-hooks.php';
	require 'inc/woocommerce/shopper-wc-template-functions.php';
}
add_action( 'user_register', 'xml', 10, 1 );

$xml = "<customer><activation-code>".rand(100000,999999)."</activation-code>
<area-code-id type=\"integer\"></area-code-id>
<billing-failure-date type=\"datetime\" nil=\"true\"/>
<created-at type=\"datetime\"></created-at>
<email>".$current_user->user_email."</email>
<first-name>".$valueVorname."</first-name>
<id type=\"integer\"></id>
<language-id type=\"integer\">2</language-id>
<last-name>".$valueNachname."</last-name>
<npvr-limit type=\"integer\" nil=\"true\"/>
<npvr-quota type=\"integer\">360000</npvr-quota>
<other-than-stb-devices-limit type=\"integer\">1</other-than-stb-devices-limit>
<phone></phone>
<pin>".rand(1000,9999)."</pin>
<pvr-limit>NO_LIMIT</pvr-limit>
<secondary-pin>".rand(1000,9999)."</secondary-pin>
<status>enabled</status>
<stb-devices-limit type=\"integer\">1</stb-devices-limit>
<updated-at type=\"datetime\"></updated-at>
<uuid></uuid> 
<external-id nil=\"true\"/>
<npvr-quota-used type=\"integer\">1</npvr-quota-used>
<npvr-limit-used type=\"integer\">1</npvr-limit-used>
<area-code-external-id nil=\"true\"/>
<language-external-id nil=\"true\"/>
<address-attributes>
<city>".$valueOrt."</city>
<street>".$valueStrasse."</street>
<postal-code>".$valuePost."</postal-code>
<province-id>119</province-id>
</address-attributes>
</customer>";


$url = 'https://yyy.xxx.xx.xx:xxxx/rest/customers';

$ch = curl_init();
curl_setopt( $ch, CURLOPT_URL, $url );
curl_setopt( $ch, CURLOPT_POST, true );
curl_setopt( $ch, CURLOPT_HTTPHEADER, array('Content-Type: application/xml','Authorization: Basic QTFDVjVsaGl5d1d2NXh3UWJ0OFE6'));
curl_setopt( $ch, CURLOPT_RETURNTRANSFER, true );
curl_setopt( $ch, CURLOPT_POSTFIELDS, $xml );
curl_setopt( $ch, CURLOPT_SSL_VERIFYHOST, false);
curl_setopt( $ch, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt( $ch, CURLOPT_TIMEOUT, 10);

$data = curl_exec($ch); 
//print $data;

//var_dump($data);
$xml = simplexml_load_string($data);
$json = json_encode($xml);
$arr = json_decode($json,true);
//print_r($arr['id']);



if(curl_errno($ch))
    print curl_error($ch);
else
    curl_close($ch);


$resultVorname = wpuef_get_field('c11');
$valueVorname=$resultVorname->value;
echo $valueVorname, "<br>";

$resultNachname = wpuef_get_field('c15');
$valuenachname=$resultNachname->value;
echo $valueNachname, "<br>";

$resultStrasse = wpuef_get_field('c23');
$valueStrasse=$resultStrasse->value;
echo $valueStrasse, "<br>";

$resultPostleitzahl = wpuef_get_field('c31');
$valuePost=$resultPostleitzahl->value;
echo $valuePost, "<br>";

$resultOrt = wpuef_get_field('c35');
$valueOrt=$resultOrt->value;
echo $valueOrt, "<br>";


$resultTelefon = wpuef_get_field('c43');
$valueTelefon=$resultTelefon->value;
echo $valueTelefon, "<br>";

$resultSprache = wpuef_get_field('c12');
$value1=$resultSprache->value;
echo $value1, "<br>";

echo 'User email: ' . $current_user->user_email . '<br />';

}