At one point, I mentioned the differences of understanding and asked in a different thread a while back if this notion of equating Gabriel with Holy Spirit is held by all Muslims. I don’t remember if I ever got a response.
In Catholicism, Holy Spirit is the third person of God. Gabriel is an Angel, big difference. An Angel is a spirit, an Angel is holy, but that does not mean an Angel is the Holy Spirit. Besides, the Angel Gabriel is not the only Angel in existence. Are you saying the other Angels are also Holy Spirit? Consider this sentence: Sherry is a girl, she is my friend, but that doesn’t mean she is my girlfriend (in the sense of being my lover). Similar logic.
I usually put capitals when referring to the one God, and not when referring to other gods (like Zeus is a god). Similarly, I also put capitals when referring to the Holy Spirit as the third person of God, and not when referring to regular holy spirits. Or in my example, the difference is in words instead of capitals: a girl friend (two words) and my girlfriend (one word). I’m not certain if all english-speaking persons do like I do, but this was how I was taught. Someone told me that in Arabic there is a difference as well: God (Allah) and god (ilah?). I apologize I have not done my research in this last one, but I just want to make a point that one’s language also plays a role in understanding concepts.
Anyway, with this logic in mind, Christians do not take Gabriel or any other Angels as the Holy Spirit the third person of God. Thus, Christians do not take Gabriel or any other Angels or holy spirits as God. If you keep claiming that we do, then I am sorry that I have failed in my explanation. Perhaps you should seek out someone else to understand the concepts in another way.
As it also has been done in a different thread, if Gabriel/Angel is really Holy Spirit as you claim, then any sentences with Gabriel/Angel should be exchangeable with Holy Spirit and vice versa. This is not the case.
As for Jesus as Prophet… Again, we seem to have a different definition of Prophet. I don’t believe we call Adam and David as Prophets like Muslims seem to do.
Lenten_ashes already answered about Mary.