"How are you doing Marcus?"
Translation:Quomodo te habes, Marce?
Think that the verb is not just "habere" but reflexive "se habere" which has a meaning like "to feel (self)". Just like French "Tu te sens bien." (You feel good). Similar structure (but just different word).
The "ne" suffix should be accepted as a replacement for the question mark, since ne was used before it was introduced