Dreaming of opening a door for someone can be both good and bad and it depends on your reaction as per dream meaning and interpretation. The dream is positive if you are seen happy in the dream. It means you will meet someone of your wavelength or liking. It also means a new relationship. Dreams of opening a door for someone and you are terrified or crying means you will be blackmailed or you can expect some kind of trouble in life due to a person whom you trusted.
Dream of opening a door for someone and you know the person means you will get into a romantic relationship. It also means you will meet someone without the knowledge of other people. It also means starting a sexual relationship.
Dreaming of opening a door for someone and it is a stranger means you will develop liking or intimacy with a person whom you had not seen in real. It means trusting someone blindly and later regretting it.
Dreams of opening a door for someone and you are not seen in the dream means someone whom you trusted romantically will cheat on you.