"A big horse and a small cow"
Translation:Een groot paard en een kleine koe
This contradicts the man/book example is the same lesson. In that example its the exact reverse even though there is a singular man, book, cow, horse. Not a good example imho - or at least provide a better build up to this het/de-word, adjective/noun, indefinite article stuff. No one learns language through complicated rules, if you could just build up better examples and repetition in the lessons I think it would help.