German qualifiers; Superlativ und Komparativ
As I think this lesson really lacks explanations (Qualifiers), I've done some browsing on the web and I found a pretty simple explanation in German (but really simple!) with a clear table.
You should be able to understand it when you reach the qualifiers lesson (I did). I hope it will help.
PS: the important exception taught in the Duo lesson is: gut => besser => beste