Not really sure what end effect you are after but you would need to remove the position:relative from .main-height and then apply position:relative to #personel instead with a z-index of 0. That will allow the pseudo elements to go underneath the main-head but stay above the white background. You can't put a positioned child behind its parents background when the parent has a z-index other than auto.
Use negative side margins to pull .main-head wide and if you want it to cover the whole white background then remove the width also.
That should get you close although you may need to tweaks the position of the folds using top rather than bottom.