Can I frame over an existing deck with a new deck to raise the level?
Not sure what you are asking, but the footings supporting the deck structure are in the ground under the posts that hold up the beams. Footing size, post size, beam size, joist size are all engineered to support the weight of the structure,and any distances spanned.

If you look at some of the other photos on the website they show posts under the outer edge of the octagonal section supporting it, its not a cantilevered section if that's what you're wondering. You just can't see the framing involved hidden under the ipe decking.