Poderiam me ajudar a saber se estou estudando corretamente?

Minhas respostas em vermelho.

Bob and I ……………. (just got/ had just gotten) engaged, so we went to a jewelry store to buy a wedding ring. We …………….(just chose / had just chosen) a ring when a man with a gun had came in /came in . After the robber …………(took/ had taken) Bob's wallet, he has demanded /demanded the ring.