// In functions.php oder per WPCode – nur auf Referenz-CPT-Seiten
add_action('wp_head', function() {
  if (is_singular('referenz')) { // dein Custom Post Type
    $post = get_post();
    $schema = [
      '@context'  => 'https://schema.org',
      '@type'     => 'UserReview',
      'name'      => get_the_title(),
      'reviewBody'=> get_field('kundenfeedback'), // ACF-Feld
      'datePublished' => get_the_date('Y-m-d'),
      'author'    => ['@type' => 'Person', 'name' => get_field('kundenname')],
      'itemReviewed' => [
        '@type'   => 'Service',
        'name'    => 'Aquapol Mauertrockenlegung',
        'provider'=> ['@type' => 'Organization', 'name' => 'Aquapol']
      ]
    ];
    echo '<script type="application/ld+json">' . json_encode($schema) . '</script>';
  }
});