Comment on Technical Support by SEO Dave.
Have you tried the WordPress Support Forums at https://wordpress.org/support/ there’s thousands of people there with expertise in various areas of WordPress who will help you with general and specific WordPress support issues for free.
It’s one of the sites I use for support when stuck on a problem as you can see from my profile https://wordpress.org/support/profile/seo-dave
Look for a plugin to achieve what you want. For the record the website you linked to isn’t a WordPress site, so they aren’t using a WordPress way to achieve what you want to do: no idea if the feature exists via a WP plugin.