Domanda!

It means Mitte and Köpenick are in that direction, 21km and 1.2km away respectively.

Generally, these are intended for bicycles as they don’t need to take the same route as the cars do, which are shown by other signs. Most of the time, it’s almost life-threatening if you do follow car signs on a bicycle, especially outside the cities.

The boat means that you need to take a ferry to get to the location. You’ll see similar signs without boats.

A bit off-topic, but you’ll sometimes see little signs underneath these and these usually designate a long-distance cycling route or some other notable cycling route.