"My two hats are red."
Translation:Meine zwei Hüte sind rot.
I think you guys have to understand with Duolingo, that a big part of its learning methodology is learning by exposure and immersion.
Think back to when you were a child. Did you learn all your English (or other native tongue) by being taught how to use everything before you used it? No, of course not - that would be impossible! You flailed around blindly most of the time, made lots of mistakes, got embarrassed a lot, and learnt from it. And you had some formal schooling in your language a bit later and concurrently to augment that learning by failure.
Likewise, one of the most successful strategies for learning a second language is learning by immersion - where you're thrown in the deep end from time to time, forced to fail and make mistakes, and learn from them. The most extreme example of this is actually living in another country.
Obviously this isn't the only approach Duolingo takes, since they try to give us some grammatical background too, and they don't throw unknown words at us without explanation too often.
What I would like to see, however, is for Duolingo to try and educate us at some point in the first few lessons about their learning methodology, why they think it works, and what we can expect. That way we wouldn't get frustrated by situations like this.
tl;dr: failure is a natural and important part of learning.