Power Assist Brake problems of the 2002 Volkswagen New Beetle

I purchased my vw on 11/21/03 the next day the I was driving car and noticed that it was not picking up speed then the brakes was really hard and it was making a roaring sound. The next day I took car into vw svc dept and was adv OH since you have a diesel car it will do that I was not tkn that for an answer I expl to svc tech that thers something wrong with my car, but they would not look at it. On 11/23/03 I was driving on a major highway and I my car was stalling and would not go pass 45 and then I smelt something burning and then smoke the brakes had locked up and I pulled over and had car towed to dealership. The dealership where I purchased it from told me that it was ok and didnt replace anything. And advised me that I was ok so I took car home and 3 days later it did it again, I took it to a different vw dealership and they took car overnight and they found that the hydl booster was bad,they replaced that and then I expressed my concerns about the brakes because they just didnt feel right to me. I was adv that OH the brakes are good and sent me on my way. About 2 weeks later I didnt trust to tk my car to dealership I took car to actor gator which was great! to check my brakes and they found problem and showed me how back brakes should look like and how mines was (there was hardly any left ) and they replaced brakes for me. Im upset that even though I purchased a used ceritifed vw from a vw dealership I felt comfortable and I didnt understand how they could sell a car with no brakes which is a safety issue. And then a customer having to pay for brakes not even a month after I got it.