It will help if you read some of the other comments on this page. You should also know that every exercise on Duolingo does not consist of a full sentence. We could use "of the breakfast" in a variety of sentences. The audio clearly says "του πρωινού" which is important because this skill is teaching the genitive.
The pronunciation is correct. "του πρωινού" is "two pro ee new" whereas "το πρωινο" is "toe pro ee know" To listen to native speakers you can try:
I think you already know this is not a full sentence. And if you had read the other comments on this page you'd have seen it's been discussed before. It's always a good idea to read the comments.
It's unfair to characterize something as "nonsensical" in a course that is older than its current team is. As it is often the case in life, you can either choose to dislike this specific exercise or keep a positive attitude and seize the opportunity to see an example of the genitive case, which is a fundamental part of Greek grammar. As you go further down the tree, you'll see that this course has lots to offer. This kind of sentences can be part of short dialogues.
That's fair, I meant no disrespect. It can just be a little frustrating to understand what is being said but not figure out how the course itself wants me to present that information. Obviously it is just part and parcel of learning in this manner. Overall I appreciate the hard work put into these language courses.