how can gravity wrap space-time when space itself is not a sheet but a volume

The idea of a sheet demonstrates gravity's affect on space-time in any 2 dimensions around an object with mass. For a three dimensional example consider a foam pad 1m cube. Gravity's effect on space-time would be to shrink half a meter in the center of the pad and stretch the remaining volume toward the center.

a foam pad gets shrinked in only 1 direction that is to the bottom ,but gravity should wrap in every direction

What you have to consider is a "swapped" principle. What would be considered as mass, in the medium we know as vacuum, would be considered as volume, in relation to your water scenario. The mass of the vacuum would be displaced by a more massive object, (say, Earth) just as if one were to drop a "decently" buoyant rock into a glass of water, the volume would be replaced by that of the rock. According to relativity, if these were the obstructions in the path of space-time (which could be considered radiating light of all wavelengths and frequencies, depending on ones outlook) they would follow the same laws of physics as everything else in a vacuum and be attracted to the more massive object. My mind really doesn't go to "how is it possible" but rather "could this idea be an insight into the term "destiny", and what are they implications of space-time doing a tango with itself?"

In other words: What happens when you put multiple sheets together? You get a book. (A volume, if you will) lololol]
What happens when you put multiple spaces together? (in the form of hypothetical "sheets," to be simple) You get a very "extended" space. Which by our reckoning, would translate into time.
Being as physics are the way they are, mass (what you have stated as "gravity") warps that. Put the rock in the water, and you have a rock in water. Not water in a rock, that's in the water. You feel me?

Gravity doesn't warp spacetime.  Gravity is warped spacetime.  Mass causes spacetime to warp in its presence; therefore, mass gives rise to gravity.

The familiar analogy that many use is the two-dimensional rubber sheet.  Placing a weight on this sheet will create a depression, thereby causing a marble, say, to follow a curved path should you roll it in the weight's vicinity.  The thing is, this "depressed sheet" applies everywhere around the object, not just what you consider to be the "bottom".  That's one of the limitations of using the 2D sheet analogy.  In reality, the curvature completely surrounds the object.

Consider this image.  It more accurately represents gravity as curved spacetime.