Really good job dude I like the Germanish style gas mask with the suit I always did like Gasmask and business suits.
The drawing is very well done and you did a great job on the gun (I have problems drawing them too) and the choice of gun makes it feel Post-apocalyptic.
After looking very closely at the drawing for about 5 minutes I haven't found a single error its flawless and almost perfect. The only reason it isn't perfect is that I personally felt that it would be better colored in.
a Very well done piece of work in my opinion you have gained yourself a fan I can't wait to see your future work.