"You are drinking a coffee."
Translation:Tu bois un café.
There is no supplement for conjugations in Duolingo. You will have to learn them on your own. It's just a part of learning a new language. There are many resources online that can help you with conjugations. For example, word reference.
Duolingo is essentially a language learning tool where you shouldn't be bogged down with learning grammar. It should ideally teach you conjugations by looking at their patterns, but it's mostly not enough. So we also must look at other learning resources.