Collapsing car interior

I bought a pre-owned CLA 200 mid November and last week when I wanted to get inside my car I noticed the car, s interior was detached from the roof of the car and it was falling inside the car. Mercedes Benz's slogan is the best or nothing. I seek restitution from Mercedes Benz for selling me a car that is faulty. This is not value for my money. I took the car to the sandown dealership on Monday and I was given a courtesy car for a day. I am sensing they will put glue on the car's interior to attach it to the roof of the car, I won't accept it. I am a woman but I am not stupid. The car does not have value at all. I am so disappointed to own a Mercedes Benz, it was always a dream of mine to own a merc until now.