Custom Module not saving and receiving data

this is code from the internet

 <!DOCTYPE html>
 <html>
 <body>

 <h1>My First Google Map</h1>

 <div id="googleMap" style="width:100%;height:400px;"></div>

 <script>
 function myMap() {
 var mapProp= {
    center:new google.maps.LatLng(51.508742,-0.120850),
    zoom:5,
 };
 var map=new google.maps.Map(document.getElementById("googleMap"),mapProp);
 }
 </script>

 <script src="https://maps.googleapis.com/maps/api/js?key=AIzaSyBu-//916DdpKAjTmJNIgngS6HL_kDIKU0aU&callback=myMap"></script>
 <!--
 To use this code on your website, get a free API key from Google.
Read more at: https://www.w3schools.com/graphics/google_maps_basic.asp
-->

</body>
</html>

Ok I will look into it. I try it out by myself and share my code with you!