Rolf,
When I began to learn engraving, I started cutting what would be considered shading lines; very fine, narrow and shallow. I just cut one line next to another, about 10 / 12 mm long, and about 0.1 mm wide and deep.
Hand pushing the graver is pretty easy cutting this small line, just be sure you're cutting a curl of metal at the tip of the graver, and not just making a scratch in the metal.
Good luck on your exams!!
John