GameMaker Problems Layering Tiles

[Sherlock]

So, I wanted to make a top down game with similar style like Stardew Valley, as a third year anniversary present for my girlfriend, going threw the most memorable memories from my point of view.
And with that I wanted to give the game some depth.
I got it working for all the instances like a desk_obj I made.
I used the End Step-Event in the Player_obj for that, which looks like this:

with (all) {
    depth = -bbox_bottom;
}

But now, instead of showing the Player beneath a tile_wall, he's now drawn above it.
I tried setting the Tilesets depth to -100 and layering it on top of the Instance Layer, but neither worked.
Just to add, I'm pretty much a total beginner. I did watch alot of videos from Shaun and FriendlyCosmonaut which were a great help, but since I dont really understand what I'm doing I can't figure out what to do.
I would honestly really appreaciate any help I can get. Thank in advance.

 

[eimie]

If your game has a resolution of let's say 640x480, your players depth will be -320 if he stands in the middle of the room. Try to set your Tilesets depth to a larger number like -1000.