Google banned you?

It´s not far from Mitte to Kreuzberg. I would think less than 10 minutes with the underground. Very easy to find and easy to use the underground too. Look for the sign U

I have never used the Hop-on Hop-Off, but I am quits sure you can get on from any point. Are you arriving at Tegel Airport or Schönefeld? Tegel is basically close to the center (6-8 minutes). In any case there will be a bus just outside the arrival terminal. Get on the bus and get off by an underground (U) I recommend you to download the map and prepare where to get on and where to change line. It´s very convenient in Berlin. The taxi´s in Berlin offers a spacial system called "kurzstrecke". Meaning if you stop a taxi in the street and travel max 2 kilometers, the price is only 4 euros. But you need to tell the driver you want this special tarif. My favorite places for shopping in Berlin are these: Friedrichstrasse (Berlin Mitte). Simply a beautiful street for shopping. In general the area Mitte is incredibly nice. Hackesche-Hoefe This area is also very nice. Many small galleries, an outdoor market, small special shops and cafes. Area around Kurfurstendamm. If you look for something upscale, you have to go to the famous shop KaDeWe. Europe´s biggest shop. 6th floor is dedicated to food and beverages. Many small restaurants, beer and champagne bars. Awesome! Good luck!