i actually live in Berlin too and while Summer 2016 wasn't that bad, i remember suffering a lot in the 2015 summer heat in an office without AC. And that wasn't just a few days, it was weeks at a time.
My office in 2015 was in an Altbau with very high ceilings and thick walls & it was nice and cool. I would still argue in favour of better insulation/construction.
EDIT: oh but transit here should definitely be better air-conditioned: I don't think there's much you can otherwise do to make subways/trains/busses pleasant once it starts getting hot.
I remember I returned from my parents where I had stayed over the weekend and it was okay - to a city that was still glowing from the heat at 11 pm at night. I say that as someone who spent a summer vacation in the Emirates (that place has cooled swimming pools right at the beaches, and for good reason the Gulf water is not warm but unbearably hot!).
In general, if/when global warming picks up we have to make some major changes to all our cities. As they are now they are giant furnaces and heat batteries with all the exposed concrete and asphalt.
