I bled, I changed the master cylinder, brake booster hose has air when I unplugged it but I still can’t figure out what’s going on. Nothings leaking. When car is off brake pedal get stiff but when car is on it goes soft, can’t figure It out help

I replaced the booster too. But I just put a tube into a water bottle cap and water bottle then put the other side of the tube into the brake front and rear nipple and just pump the brake then hold it in and loosen the nipple then repeat.

Try gravity bleeding starting at the caliber furthest from the master cylinder

when the car is off, the first few press feels soft then gains pressure after the first few press. If I stop pressing it for a few minutes, it restarts and it’ll be soft again but gains pressure. When you turn the car on, it suddenly loses that pressure and goes soft all the way to the floor but it will come back up.

Never mind, I found out why. My brake calipers was upside down on the wrong side. I put the left one on the right and vise versa. The bleeder nipple was facing down when it was suppose to face up.