low poly shoulder problem

Hello! i have problem with low poly shoulder.

My goal is to make low poly character like this l4d reference and also to rig and animate it.

This is my current situation and i dont know how to proceed because i dont have good example picture to see it more clearly…

Here is also my blender file if it helps to see what im doing n00b.blend (453 KB)

This is my reference and my goal