Why you are still using 2.79 version? :)
You don't need so much polygons to represent helmet geometry.
Also topology is too dense in some places. On both parts: helmet and glass same issues.
1. Unnecessary edge loops because they do nothing with geometry. Only will slow down performance in game engine.
2. Too dense topology. Better use "Mark sharp" + Edge split modifier.
Fine result for 1 hour. Next time try achieve same smooth shape with at least 5 times less polygon count (and in 2.8 software version). :)