Hi! I have update all plugins but I do not see that functionality. Where can I see it? I need to configure something in CB GALLERY?

There's nothing to enable. The preloading behavior is just built into it.

Now in your demo the window modal gallery is faster!!! How did you get that? I like two or three seconds faster than some days ago! =) ...

It's because it requests the image src and the modal window contents at the same time. This is the preloading behavior implemented in latest build. CB Gallery also of course leverages browser cache. Once the image src has loaded the browser will cache it and load from disk cache instead of requesting it again.

Is there anything else that you can do to make it faster?

At this time, no. However we're always improving our code to be more optimized as often as possible.

Do you think there is any chance try to change that modal window in order to have the image and below thumbnails?

No, and it wouldn't improve your performance either. The images still have to be loaded, which on your site specifically is slow which means the issue is very likely isolated specifically to your site.

I think it would be great and will load the image instantly.

The HTTP request is loading instantly. Your site is just extremely slow sending the image. I'm guessing you're not using PHP7 and/or your host is inadequate for what you're trying to do. Could also just be something installed slowing things down. There are access and permission checks that have to be made so the images can not be accessed directly.

Could you help us with optimization of our website in general?

We do not provide such a service here, sorry.