Brake Master Cylinder problems of the 2014 Volkswagen Jetta

I bought a 2014 new Jetta se. But this vehicle sits in vw dealership for entire first month. Last week, I had a fender-bender accident on local highway due to brake problem. Two claims involved in this case: 1. Brake hard like rock when I try to start the vehicle in the morning. I could not start the engine. 2. When I drive on the 50 mile speed limit high way, I could not stop the car due to weak brake system. It took extra long deep stroke to stop the vehicle and took extra long distance to stop. Also I could not do emergency stop if some cuts in front of me. Weak weak weak brake. . . . . I drove for more than 20 years, I have never had such experience. It is an unsafe car! my wife now refuse to drive it. I took this vehicle to vw dealership and they find out problem with car (faulty booster and master cylinder). They changed the components and system twice, and now condition is the same. Vw technical service went to dealership, and they told my dealer that this vehicle is safe. . . . . I am very shock on this conclusion. Please investigate on this vehicle brake system. I don't want other vw Jetta drive have the same problem, rist life for a faulty system, and I must voice it out to warn my fellow Jetta driver: be carefull!.