Your suggestions please, for tour ended things to do, which you did, including near tour hotel, and beyond things recomended in Rick's Berlin Guide book. We will be staying at tour hotel for four nights following the end of the tour in September, Thank you
If you are interested in seeing historic sites in Berlin, I mean traditional historic sites prior to 1933, go to eastern Berlin. Basically, historic Berlin is eastern Berlin. You could do your own Berlin itinerary regardless of what RS suggests based on your own priorities instead of strictly following the RS program. I don't use the RS book on Berlin at all.