"You eat a big bread."
- pain is masculine => "grand" and not "grande"
- adjective placement: pls read this: http://french.about.com/od/grammar/a/adjectives_4.htm
As I wrote earlier about "pain", in a number of French regions "un pain" is a specific kind of "bread", ie a longer and larger baguette (@400g vs 250g). Therefore it is possible that someone eats "un grand pain", at least grammatically. However, chances are that only an ogre could eat "un grand pain".
Yes, you're right, I didn't think about that. Anyway, if we were really speaking about « un pain » as a type of bread, I think we would need a more appropriate translation than “a big bread”. I found “a loaf of bread” for « un pain » in my dictionary; maybe that would be better.
Makes sense to me. But I think Duolingo shouldn't consider a sentence correct just because it attempts to mimic the structure of the target language--it has to convey the meaning in natural language. "A big bread" is not grammatical English. A loaf of bread makes sense. This online dictionary clearly says that "bread" on its own is a noncountable noun in English: http://www.learnersdictionary.com/search/bread
When I started studying foreign languages back in high school, I learned very quickly that a thorough knowledge of one's native language is invaluable when learning a new language--and conversely, studying a different language is often a great way to become better acquainted with one's mother tongue. I'll always be glad I studied Latin!