Translation:On every Simchat Torah he dances until the morning.
Native English speakers do not say "until the morning." We say "until morning."
"do not" as in never? Not quite, but Americans tend to use "until morning" more.
The British tend to use both approximately the same amount:
Another English mistake of yours. I wrote each simchat instead if "on every" and was marked "wrong". Mine is correct. You are not native English speakers, that's obvious.
Who is "you"? The people who created the course created the Hebrew sentence and then provided one or more English translations. Everyone who makes a different translation (like yourself) gets it marked as wrong. You can report it, and if the people maintaining the course agree, your translation is added to the list of correct ones.
The "on every simchat" is also correct, and native speakers might say it. I think simply saying "Every simchat" is more common than either your "each simchat" or their "on every simchat". Similarly I think "until morning" is more common than "until the morning". I think they should all be accepted.