Not sure what roads you have there in Berlin, but in many parts of America we have lots of dirt roads. Not offroad, but also not paved, these are just regular residential roads in many areas once you get out of the suburban areas. 28mm is painfully narrow and while I have ridden as narrow as a 23mm tire on some of these roads, it requires caution. XC tires will work but are more than needed and won't fit most gravel frames anyways. Especially not those with road like geometry, which is what I want for this riding. In between, in the 35-45mm area is about perfect. Enough tire to handle the bumps, not enough tread to slow you down. The basic goal is to have something that behaves like a road bike for these unpaved roads.