I listen to the intonation and I really don't hear it as a question. Are there any intonation lessons anywhere? I know again Duolingo puts the question mark in as a clue but that's not going to happen with someone speaking. Or am I missing where the 'Do' is?
The TTS audio leaves you clueless but questions ought to have different intonation. When you have some question word, it has some implications on the word order but otherwise not really, I don't think a sentence would change spontaneously apart from intonation.