Oi gewalt!
nms1 sounds like the typical German who expects to have everything done for him and is indignant when this is not the case.
As Bremen said: 20kgs are the norm - you receive a lot of paper with writing on it that tells you the conditions of the ticket, flight, Warsaw Convention and the rest.
When you rent a car do you expect the car rental company to give you details on consumption, boot space, petrol pricing and how to care for the upholstery?
please tell me how my girlfriend and I have to pack for 6 months and have only 40kg together???
You are correct, of course. I believe the airline should be held responsible for not allowing you six months worth of clothing, food, appliances, furniture, those Bavarian soft-porn flicks of the 70' and hair care products - as well as a six months supply of complaint forms as you are starting your trip off well.