Kathrin, thank you for the advice! If shops are closed on Sunday, then it will be sightseeing day then. I booked an apartment for 2 nights in Freiburg already, now looking for another place for one more night. It's quite hard to find a decent place with reasonable price in Basel for 5 (either an apartment or a room for 3). We considered booking 2 rooms (1 room for 2 and another for 3, but not many hotels offer aroom for 3)