Duo is trying to teach how languages work and how to use them.
For stock phrases to use in short term situations, you would probably be better off using other approaches. Duo will teach you whether that stock phrase you want to know has a barely noticeable component that tells you whether the intent of the phrase is directed to you, someone else or himself. Duo will help you understand that when you hear something about......ooooo fooo......, he is saying something about where the traffic light is. If he you hear something about .....oh fooo.... he is telling you the place is on fire. Duo teaches you to recognize these and other differences by placing them in a context where, because they are often not easy to distinguish, you have to know and understand them to be able to hear them.
If you want straight vocabulary builders try Memrise. Anki is a flash card system which offers prebuilt decks of cards, one of which is the one thousand most common French words. Both are free. There are any number of commercial options which offer to teach you phrases that they believe will be of assistance to tourists and such.
The trouble with the stock phrases approach is that one man's stock phrase is another man's useless sequence of words. I haven't been to Paris but if I go, it seems highly unlikely that I will be asking "what aisle is the butter in." However, I can easily imagine saying something like "why are all those butter producers demonstrating, blocking the streets by dumping manure and generally making life difficult for citizens and tourist alike." In my city, I have had more that a few occasions to say something about where the traffic light is, (traffic control signs are usually where the traffic light is, you are there when you get to where the traffic light is etc.) I have not yet had occasion to yell fire. Yet I imagine very few of the services teaching you stock phrases will provide assistance on dealing with traffic lights, mass demonstrations or many of the things that actually come up for tourists.