Εγώ θέλω ένα κρύο καφέ
This sentence is translated in Duolingo as "I would like a cold coffee" whereas I believe that it should be "I want a cold coffee". I believe that the correct sentence should be "θα ήθελα ένα κρύο καφέ".
Remember, καφές is masculine, therefore 'θα ήθελα έναν κρύο καφέ'. :)