Website became very slow after adding google ads

I have a website and it became very slow after added google ads and its script. Can someone please tell me what is the issue and how I can make those ads script fast to load the page?

I am using the below script to show google ad on my website page.

<script async src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script>
<ins class="adsbygoogle"
  style="display:block"
  data-ad-client="ca-pub-AD_ID"
  data-ad-slot="SLOT_ID"
  data-ad-format="auto"
  data-full-width-responsive="true"></ins>
<script>
(adsbygoogle = window.adsbygoogle || []).push({});
</script>