I’m stuck with a lemon purchased from car max any suggestions?

Feb 17th purchased Buick envision 32,000 miles test drive ot twice on separate days. A week later car was making odd noises turns out a tsb bulletin determines faulty motor mounts car max send the car to Buick car still under manufacture warranty (something they didn't tell me didn't find out until repairs was needed) get the car back transmission starts to stall on take offs. A week later the car completely loses power. I was traveling about 40 mph I came to a complete stop at a traffic light proceeded to make a right turn gave the car some gas it does a noise dive stalls I tried to press the gas pedal goes to floor seconds later car violently jerks I take to car max they say we see nothing wrong we will ship it to Buick. Buick is telling me they test drove it nothing happen. I'm so frustrated I'm afraid to drive the car in fear it's going to stall again with my kids in the car.