Many Duo sentences sound odd, often because there is no context. But if we were working with paragraphs we'd likely never get through one without losing a heart. ;) "We'll sell the shoes, but those socks will never move." Presence/absence of articles is confusing. Thankfully, native speakers I have encountered in "real life" are very understanding. Sometimes when I ask if it should be "queso" or "el queso" the answer is a shrug of the shoulders, a smile, and a "whatever."