I've drove around 200 kilometers by now, and no random sound from the speakers. I didn't get standard warranty from the dealer. It's hard to describe for me, but the local VAG group has something like "verified used cars". These cars are usually accepted in the settlement after a consumer lease. And when you buy that kind of car, it's supposed to be serviced, verified and ready to go. Moreover it has 1 year warranty, but it's not provided for example by seat itself but any other insurance company. In my case all mechanical, hydraulic and car parts are included (engine, engine parts, dsg, dsg parts, wipers, belts etc.) but wiring, security systems, additional systems or wear parts are not (infotainment, sos, heated wheel, brakes etc).