On Sunday afternoons, Mauerpark is the website of a flea marketplace with musicians and meals carts. This is the best time to go to. Germans are still really ashamed from the nation's 20th-century record; it’s a delicate topic, and locals are likely to stay away from speaking about it. From https://chippz.de/sicherheitsdienst-berlin-ihr-verlasslicher-partner-fur-schutz-und-sicherheit/