Can anyone recommend a Catholic mass Saturday evening somewhere near the hotel Hotel Kastanienhof?
Google Catholic church Berlin. Using English Translation app, you can find mass schedule for various churches in Berlin. The only Saturday evening I am seeing is at St Boniface near the Mehringdamm U-Bahn station on the south side of Berlin.
The cathedral of the bishop of Berlin, St Hedwig, has
a regular saturday evening mass.
Details here: https://www.hedwigs-kathedrale.de/gottesdienste-und-beichte/zelebrationsplan/