We didn't get to stay in Herbert and Irina's apartment due to kitchen renovations, but he offered us a very nice second apartment without any extra charges. The apartment was perfect, an easy 10 minutes from the U-Bahn or from the S-Bahn. You're in the center of Berlin in about 25-30 minutes (I never actually timed it though). Herbert and Irina were so welcoming and provided us with recommendations to local restaurants. They were very communicative and some of the best hosts I've had on Airbnb. I wish we'd gotten more time to talk with them, but it was a short trip. You can't go wrong if you stay here!