Is there a difference in pronunciation between the "ch" and the "tr" sounds?
It is not impossible to make a question of an English sentence by intonation but this usually involves stressing the element that is being questioned. To do this with two words conjoined would produce a very unusual sentence that would probably not mean what the Vietnamese sentence means.
Neither do I... I often dont hear the accents as they're supposed to be used. So i just kinda copy how it sounds :)
"I am FAST OR SLOW?" would probably be a response to a statement and would be roughly equivalent to "What do you mean by saying that I am fast or slow?"
"Hay" may mean "or" or "interesting". I wonder how that came to be. And could you use same word twice in a sentence to mean both things?
... and yes, of course you're right with hay, I also wonder how it came to such different meanings (probably there is no connection at all) and I'm also curious to know if both words with different meanings are possible in the same sentence! Maybe possible but not elegant?