1990 Plymouth Voyager Brakes

Hi PLEASE help I had this van for 2 days and it is giving me problems the brake do not work at all. I recently drove the van in the freeway and almost got killed decided to fix my brakes the mechanic came to my home and changed the following changed the brake pads, and the master cylinder the mechanid bleed the the line and the wheels but he has worked and the problem is still there when we push the brake pedal it goes all the way to the floor when the car is off the pedal it seems to get harder without but as soon as we turn it on the brake pedal goes back to the floor he does not have parking brake on and it seems he has done his job does anyone have any suggestions for my problem thank you.