You can differentiate questions and statements by the punctuation. If there is a period, it is a statement. If there is a question mark, it is a question and you have to rearrange the words a little bit to get it to make sense in English. Always try to look at the punctuation, and it will help you a lot. :)
So the "u" in uccello is completely silent? I heard phonetically (eh oon chell low) and I am wondering why I didn't hear (eh oo noo chell low) or (eh oon oo chell low). I must admit, it sounds better when you completely drop that first "u" in "uccello", but I want to be sure it's not just an artifact of the robot voice.
The "u" is practically silent after "un" otherwise you'd have to stop after "un". As you said "eh oon oo chell low". If you had "the bird" (l'uccello) you'd hear the "u" clearly (loo chell low).
On this post I give, along with some general info, the dictionary link for Lexilogo. There, you'll find other choices to listen to the sentences and individual words. And some are really clear and slow. Of course as with any mechanical translation site you need to take care with the translations, they can be pretty funny and sometimes completely wrong. But the pronunciation is good.
Do check out and bookmark the Guidelines.
Thanks! Regarding pronunciation, have you noticed that the mechanical voice with Duolingo Italian says l'uva like (loo bah) with a strong "b" sound instead of a "v" sound? I believe that the Italian "p" and "v" are made with the lips loosely pursed rather than the more definitive English "p" and "v", similar to Spanish so "v" might sound much like "b" in some cases, but the Duolingo robot woman voice seems to actually be saying a hard "b", not "v" at all, when saying "l'uva" (at least it sounds that way to me).
Why would there have to be a stop after un? A vowel flows perfectly with a preceding n, at least in my perception, it just creares an extra syllable. Unless a u in spoken Italian always starts with a stop - no pun intended -, which seems however not to be the case in 'é una...'. I can see a case for contracting/dropping the 2nd u though, just not because it involves a stop.