Imitating "Hitman Go" icon

Recently I'm really obsessed with the iOS game "Hitman Go" https://itunes.apple.com/us/app/hitman-go/id731645633?mt=8
Here's my attempt to make that game icon, using Sketch.

This is my very first time making non-flat icon. I can't find any helpful tutorial to get what I'm trying to achieve, so I basically just adjusting the settings in Sketch here and there.

Any critic is welcome :D Please tell me where I can improve it. I'll be very appreciated!

If you are interested in the .sketch file, let me know.