"The good-looking model speaks Swedish."
Translation:Den snygga modellen talar svenska.
Whenever you have an adjective describing a noun, you also need an article or a pronoun. All of them need to be either definite or indefinite. It's redudant, but there's no way around it. Some more info here: https://forum.duolingo.com/comment/26420394/Answers-to-some-common-questions-on-grammar-that-beginners-have