Do you think Mozart actually said this?

One of the first really good biographies of Mozart was written by Marcia Davenport. It's very sympathetic and readable – see if you can find a copy in a library, or from a used bookstore.

intriguiging how mozart & b'oven expressed how their inspiration produced their work
,,mozart "I know not where it comes from,but quickly I get from beginning to end,the whole work every note,and must find a notebook quickly to put it all down before losing all,'
beethoven.."I walk,pondering about much of nothing,and a theme occurs to me,I get a second part of the theme,across the whole orchestra.woodwinds first,then the celli,and I keep the few notes on a piece of foolscap in the pocket,return to the apartment after lunch,and continue working at it,,doing rewrites,revisions,many of these,until I have the whole thing as perfect as I can manage'
mozart heard beethoven play when he was a 12 year old,
he said 'someday this young man will make a great noise in the world'
is sounds like a smartssa thing mozart would say,,

Leopold gave Wolfgang quite a bit of help.

I doubt it since I don't believe he spoke English.

Could be that he did!! Although some people take this conversation to be an insulting answer by Mozart, it seems he gave his answer in that reply. It's an interesting way of saying; he had an inborn talent; that perhaps he didn't bother to question; as he was fulfilled by the music and passion he felt as he composed and played! He didn't question the beginnings of it, or the mystery; he surrendered himself completely to it. (just wondering, he didn't get stuck with the question of 'how?"