Admin side preloader

Hi to everyone.
I’m not a developer and I’m looking for a small help.

I manage some WordPress websites where

• on the front end a plugin show a loading animation for each page and internal link clicked.

Example if user click on “about you” page, as soon the link is clicked a pre-loader animation is showed and is also showed during the loading of the page. There are two plugin that support this function to show pre-loader also when a link is clicked not only on page loads and they are:

the free one Loading Page with Loading Screen

the paid one: LoftLoader but only on the pro version.

Now my issue is on the WordPress backend. Admins do the login on the website and are redirected on the website main page then, when they click on the admin bar dashboard link, it takes long time to load the WordPress custom Dashboard that I use.

I looked for a code to show the pre-loading also on the backend of WordPress and fount that code: link to stackoverflow code

This code never show the preloader as soon the link is clicked so is not resolving my issue as the loading are showed after a long waiting server time just 3 seconds at the end of the new page loading. Any solution to edit this code to show the loading screen as soon the admin dashboard and all backend links are pressed?

Thank you!

The page I need help with: [log in to see the link]