Both pilots were well trained, experienced Lufthansa pilots. They knew what they were doing. I would wait for more official answers, whilst the silence sounds like a loud confirmation. I don’t know their protocol, i.e. if one of the flight attendants is able to access the flight deck in case of an emergency as pilots could be
incapacitated due to toxic fumes
Is there any possibility that actually not a pilot, but a flight attendant banged on the door after noticed that the aircraft is descending towards Alps?