83 733i soft brakes(right to the floor)

So i have an issue with the brakes

the pedal used to go right down to the floor and would barely stop the car from a crawl, in response I have bled the brake lines to all calipers, and checked the hydro booster fluid level, and with only slight improvement the pedal almost hits the floor.

i am thinking the brake master cylinder is shot.

but before i go out and spend mopney i want to make sure im am getting the rigth part.

the pedal becomes solid after about 15 pumps when off, and holds pressure, when on it takes several pumps to build any sort of pressure and cannot be built up to the soild point, and looses pressure quickly when just holding the pedal down.
any suggestions?
thanks

COULD BE The brake booster $$$
LGE-LG290C/1.0[TF268435458412759924000000014802434113] UP.Browser/6.2.3.8 (GUI) MMP/2.0

I seriously hope its not the booster but wouldnt doubt it with my luck, both the booster and the master were replace about 6 years ago, for either to be gone already is a shame.

power steering works well, and makes no noise, the booster seems to function correctly, but as i mentioned in my initial post, what should the canister with the ATF in it act like when the car is on should it be able to build pedal pressure/canister volume right up like it does when the car is off

are there any test that can be done to verify the booster as working or not

The master cylinder was the problem, after replacing it I had to replace almost all the brake lines as they blew out with the good pressure, now I have brakes again!