1999 BMW 540i

Initially, my radio volume when low even after an attempt to increase the volume. Then, abs, traction and brake came on yellow. My dash board light dime out, the car started slowing down. I immediately turned off headlight and the volume off radio came back on for a while and went back down. I stop and turn off the car, it wouldn't start, but dash board light comes on and off ask I turn the key by attempting to start the car. I had a new alternator installed 2 months earliar. And the batteries is less than 1 yr old from a certified bmw dealership. Somebody help me please!