I'm sorry it didn't work for you @riccardosuardi
I think you will have to study how to use Hype first. There are so many things that are wrong with your document I wouldn't know where to start. My biggest advice to you is to not just copy and paste what you think are solutions to your problems. Most of the examples that are shared here in the forums are not necessarily suited to everyone's projects. They are just a beginning to learn how to do something and very often they need adapting to your project.
After looking at your project there are so many things that are just copied in, it's a jumble. I see you've put in the "sticky" solution from another post. You have put body and html tags inside the head HTML. You haven't called any of the scripts, on Scene load for example. etc, etc.
Finally you didn't actually use my example AT ALL! So of course it wouldn't work.
This is an adaptation of your document (I have cleaned it up).
DoveStudiare-vDBear.hype.zip (2.9 MB)
This won't always happen as it takes time that I cannot really spare at the moment.
The "sticky" footer happens when the "trigger" element (the COMO FUNCIONE element with id "trigger") hits the scroll top (top of window) this moves the footer element and changes it's display and positioning and plays the animation (again NO ANIMATION was done. I added this )
Enjoy. Unfortunately I won't be able to adapt any more. If you break you fix