Hi,
We use WP Engine to host all our demos (https://wpengine.com/). The performance of your website can also be improved, like our demos, by WP Rocket (https://wp-rocket.me/). Finally, we may also recommend Imagify (https://imagify.io/), to shrink your images with lowest quality loss.
You can always add more stuff to improve your page loading time but this is a pretty good start.
Please be aware that too many plugins will considerably slow down your page loading time. So, we advise to stick to the bare minimum! 🙂
We hope it helps.
Cheers,