Schloss Charlottenburg, a Baroque palace and garden, is just a 10-minute walk along the river Spree. Several art and history museums are also close by.
In the summer, enjoy the riverside beer garden with the locals. Take a pleasure boat to lakes in the west or to the middle of the city. Or walk or bike along the river to the Tiergarten, a large forested park, and continue to the famous Brandenburg Gate (Brandenburger Tor), the government quarter, the museum island, or choose among the enormous number of other sights in Berlin. You’ll find plenty of information in the apartment as well as on:
https://www.visitberlin.de/en
https://www.visitberlin.de/de
https://www.berlin.de/tourismus/
https://www.berlin.de/en/tourism/
For a different kind of shopping experience: https://www.theguardian.com/cities/2019/apr/29/are-the-hyper-specialist-shops-of-berlin-the-future-of-retail