pixel_player136554110 When you do this part you need to stay off of the red tiles. What nobody seems to tell you is that means Diggy can't step on the red tiles AND he can't push any of the stones onto the red tiles. If either of these things happen then you have to reset the whole thing and start from the beginning. That means making certain nothing is on the red tiles and then walking around on the red tiles until all of the gates have closed. If you don't restart from the beginning this way then you won't be able to open the gates properly, at least not that I have ever been able to work out.
This first link shows how I placed the stones to open the first set of gates. To make it easier to place them I simply dragged them to a blue square next to where I needed to place them, walking around on red tiles if necessary to do this. That way I could be certain the gates were reset to closed before I began moving the stones in place and I wouldn't have to be avoiding the red tiles so much for the first part of the stone placement. Remember, though, that once you begin moving the first stone into its proper place you need to stay off of the red tiles.
This second link shows where I placed the stones to open the last gate. Again, remember to stay off of the red tiles when dragging them into position, and that means Diggy can't step on a red tile or move a stone on a red tile.
The way I set up the first positioning of the stones makes it fairly easy to move them into their second position without much hassle. Good luck.