My car shuts down every time we slow down or step on the brake why? Help plz

Hello, This could be one of many problems. Because it happens when your vehicle is slowing and when you press the brakes, it is hard to say the brakes have anything to do with the issue, but it could be a large vacuum leak on the brake booster. Try pinching the large line off to see if you get the same results. Be cautious, the brakes will be very hard to press and less effective. Otherwise you have to start looking at engine control issues, and, in lieu of having a good scan tool, I would read the trouble code history and check on the EGR and IACV systems.