See that the brakes are operating front and rear. Drive the car hard applying the brakes and then get out and touch the 4 wheels they should each be hot/warm if the brakes are operating properly. There is a pressure gauge that can be put in place of the brake pads to verify pressures at each caliper. With wheels off the ground and vehicle properly supported spin the wheels and get some one to gently apply the brakes making sure the brakes apply evenly at each corner of the car. If you still have doubts get the brakes inspected properly by a professional.