A major part of the problem is your topology is very irregular.

I am guessing the sharp edge is because you have two edges on top of each other. For now try this - mesh > cleanup... check the apply to all polygonal objects radio button, then go to the remove geometry section and select lamina faces, nonmanifold geometry, normals and geometry, edges with zero length, and faces with zero area and then apply and it should remove any geometry sitting on top of each other as well as clean up other bad things.

You really want to strive for evenly spaced edges that form quads and flow along the natural curvature of the head. Since the helmet is hard and will not deform you do not have to follow musculature for deformation but it may be helpful.

This might give you some tips on better topology...

https://www.cgarena.com/freestuff/tut...et/helmet.html