There is lots of Berlin info on this site already, but here is some info from my experience.
There are 2 street walking areas that i know,
Oranienburger Strasse, after 9pm there are lots of dressed up good looking streetwalkers, but its stricklty tourist bait, they promise to take you to a room and do all sorts for 80 euro and then upsell like hell in the room.
All youll get for 80 is a bj with her clothes still on, more like 200 for a proper go at it.
Kurfurstenstrsse right by the U Bhann, ordinary plain streetwalkers mostly Hungarian, they take you in the nearby video cabins, 5euro for the cabin and porn, 20 for a bj 50 fuck, dirty and nasty but fun if you like that sort of thing.
I know a couple of All you can Fuck places, King George and Caligula, 100 euro gets you unlimited drinks and and fun with the ee girls on site, the quality of the girls is poor and caligula can be busy.they take you in a room for 20 suck and fuck.
Look them up, Airport Girls is the same, it right by Schonenfeld Airport
Then you have brothels all over the place, pleny of info on here.
Hope that helps