1 - Ghost =/= Possess Type. They are two different types. However, they do share the exact same type chart - weaknesses and immunity to Normal attacks included. You probably got hit with a mon that has the Scrappy ability or Innate. I recommend making a habit of checking Innates in battle using the info key.
2 - Because they are two different types, Possess types do not naturally gain STAB on Ghost moves. However, this is offset by the Distorted Innate, which effectively gives them the STAB back on Ghost moves.
