I finished all the badges. Now what?
Is there more? I finished Navajo and feel like I still don't know much.
Navajo is a brand new beta test language, so it's really not in a position to be anyone's main focus on here at the moment. Over time it will grow and you'll have the opportunity to do all the new lessons, though (the other new beta language, Hawaiian, added 9 more lessons this month).
In the meantime you can do Spanish or one of dozens more languages. It gets addictive, as you can see from all the people with multiple flags next to their name.