Thank you for posting the URL to your web site.
while this DIV
...
doesn't work
There should really be no need to modify any of the code generated dynamically by the 'juicebox.js' JavaScript file (for example, removing a class name from a gallery container) and I'm not sure why doing so should work. (I would have expected that it would cause more problems than it would solve.)
In fact, I viewed the gallery on your home page before you removed it (I was planning on taking another look at it later) on a couple of different iOS devices (in Mobile Safari and Mobile Chrome under iOS 6.1.6 and in Mobile Safari, Mobile Chrome and Mobile Firefox under iOS 9.3.1) and the gallery seemed to display and function fine in all browsers on both devices. The gallery expanded from the Splash Page as expected, the images displayed OK and the gallery could be closed to return to the original embedding page.
it doesn't work (i tried also with my smartphone)
Could you please explain what you mean by "it doesn't work". What exactly happens (or doesn't happen) when you try to view the gallery?
Also, what smartphone are you using (make and model) and what browser (and version number) do you see the problem in?
(Using a browser extension to emulate a mobile device may not give 100% accurate results.)
As it seemed to work OK on my own devices, maybe clearing your own browser's cache before reloading your web page will help.