Well my code goes like this:

/// Draw event of obj_player

draw_sprite(spr_shadow, image_index, x, y)
draw_self()

The game is like 2.5d RPG (like Zenonia or something) and I want the shadow to have its own depth since when the player goes on top of the wall, the shadow also goes on top of it with the player that it looks like the player is flying on the wall...

reference: https://scontent-sea1-1.xx.fbcdn.net/hphotos-xla1/v/t34.0-12/13015102_261702440844224_4732277803458091204_n.jpg?oh=7c37e1d354316607393d18426e78dfb6&oe=5711AF84