I'm rendering cesium 3D map but he issue is it is loading slow, Can i reduce the lag time

i'm using these scripts :

<script src="https://cesium.com/downloads/cesiumjs/releases/1.84/Build/Cesium/Cesium.js"></script>

<link href="https://cesium.com/downloads/cesiumjs/releases/1.84/Build/Cesium/Widgets/widgets.css" rel="stylesheet">

Sandcastle Link

On live server sometimes it take 30 seconds to load the map.

Any solution, Thanks