Buick brake problem?

Question

when you go in reverse and then go foward the brake gose to the floor

Answer 1

My guess is a bad master cylinder,not really that big of a job,but take it to a trusted mechanic.

Answer 2

You have a huge problem. I would say it is probably hydraulic in nature. It could be internal or external. Either way, it should be looked at and fixed by a licensed pro. Safety first. It has to be inspected to determine what's wrong.