Łukasz

I would imagine that this is simply a full width background image with parallax effect turned on. This feature is accessed through the row formats option at the top of the page in step 4

You can select one or many rows of cells, then add a picture or slideshow, or even a movie to appear behind the cell content. You can also choose full width and or parallax.

I have pointed your other 2 posts to this one (I assume they are all related). It is better to only have one post per subject, otherwise questions can get overlooked.

If you still have questions or I have misunderstood, please advise.