Friends, I need to make a parallax effect exactly like this gif, with 4 sessions. Can someone help me? I don't even know where to start.

Basically the first, second and last sessions would have a height of 100vh. The third would have dynamic height, according to the amount of content.

The sessions would be covering each other and the one that is covered would be shown as the screen scrolls.

If possible (and if not, that's fine), I would also like to do a black overlay effect before showing the session underneath, like in the gif.

Here is an working example, but I need it without the sticky effect.

Thanks!