First post ever 
I’ve been working on this scene for a week or so and this is what i did so far. I need suggestions on how to make it better because it doesnt look much realistic imo.
Here’s a few thoughts:
The original building probably had a window opening or or two. Perhaps add an upper story window in the right wall with the bricks above it collapsed.
Your representation of a collapsing brick wall probably isn’t very realistic. When a lower brick falls out, usually the bricks above it fall as well. That isn’t what you see along the left edge.
The wall itself is fairly plain. I’d expect to see a column or two, or perhaps some indication of a second floor.
I’d put a solid block lintel above the door opening to support the gap.
I would suggest adjusting the lighting…it’s almost overpowering, especially on the side facing the ‘sun’. Something like this makes me think darker, more ominous. Perhaps change the world material to a sky texture and change the angle of the sun.
Also, the brick/stone pattern would have quite a bit of overgrowth. I would either add a second texturemap and overlay some mossy textures, or add some vines crawling up the side…or both 
Lastly, if the stone is in that bad of shape, the wooden bridge sitting in the water wouldn’t fair any better…weather that some and give it the same level of eroding as the bricks.