I would like to know how to remove everything that is not in the eye, except the eyebrow.
In comments user Billy Kerr suggested a Clipping mask. It should be quite foolproof as long as you do not try to use some internally complex already existing part as your mask, but draw one for that purpose. I crunched together something that slightly resembles your drawing, but has separate colors for easy communication:
Select the orange, green, brown and black part, Group them and arrange the group to back.
Draw on top with the pen a new shape - one single closed path to be used as the clipping mask. Disable snapping temporarily if it is harmful.
Select the new shape and the group. Goto Object > Clipping Mask > Make
send the clipped group to back
If this doesn't work, your image is more complex than I have guessed. The only way to remove the need to guess is to provide some exact info of the structure of your image. (a copy in outline mode and a screenshot of expanded layer panel for a start)