Ihre Webseite,
Ihre Daten.

<iframe
  src="https://bundaris.de/api/public/v/Ihr-slug/embed/events?count=5&theme=light"
  width="100%" height="400" frameborder="0" loading="lazy">
</iframe>

<?php
$slug = 'Ihr-slug';
$json = file_get_contents("https://bundaris.de/api/public/v/{$slug}/events.json?limit=5");
$data = json_decode($json, true);

foreach ($data['events'] as $event) {
    $start = (new DateTime($event['start_at']))->format('d.m.Y H:i');
    echo "<div class='event'>";
    echo "  <h3>" . htmlspecialchars($event['title']) . "</h3>";
    echo "  <p>{$start}</p>";
    echo "</div>";
}

const slug = 'Ihr-slug';
fetch(`https://bundaris.de/api/public/v/${slug}/events.json?limit=5`)
  .then(r => r.json())
  .then(data => {
    const html = data.events.map(e => `
      <div class="event">
        <h3>${e.title}</h3>
        <p>${new Date(e.start_at).toLocaleString('de-DE')}</p>
      </div>
    `).join('');
    document.getElementById('events').innerHTML = html;
  });