Hi Anis, have you seen the helmet tutorial dones by lyes here:
http://moi3d.com/forum/messages.php?webtag=MOI&msg=2042.1

Also it seems that you posted a different tutorial here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3500.1

Are you looking for some different technique than what was discussed in those previous posts?

One key thing is probably to not worry about the face cutout area at first, instead focus first on making a full dome shape and then trim or boolean out the face area rather than trying to incorporate that outline into the initial surfacing.

- Michael