There are many things to do in and around Konstanz:
If you enjoy a nice biking trip, you've come to the right place: Around Konstanz and the lake you can find several nice routes of varying length. You can find detailed information on different cycling routes here. There are also a couple of shops where you can rent a bike, but keep in mind that the end of July is high tourism season so be sure to book earlier rather than later. We have compiled a list of shops here.
You can also choose to take a trip to Meersburg, which you can reach easily by a scenic boat or a ferry ride.
A bit further away is St. Gallen with the beautiful St. Gallen library, a must for any linguist.