So Gabriela told Muhammad without a single mistake what to say.
So if this is true then it is Allah only talking here.
Allah should 100% of the time refer to himself as one, not we.
Now if somebody is telling a story like Muhammad did then using the "we" makes much more sense when using the third person because then it is not what Allah is saying but what Muhammad is saying.
So what you have is the words of Muhammad not Allah.