Problem comes up with every redstone contraption

Whenever I try to make a redstone circuit or contraption, I come up with the same problem, a lot of the time with flush piston doors. I need the timing to activate piston A, then piston B, but when I turn it off to deactivate piston B, then A. This problem comes up in every single redstone contraption I try to make and has made me stuck unable to progress with my redstone builds. Please help. Also, for example, I need the timings in the specific parts to be the same like I need the double piston extender A to work before a normal piston B, but then Piston B needs to turn off before double piston extender A, while keeping the timings themselves inside of the double piston extender the same, (2-4-0), etc. Please help in any way, it is much appreciated.

Sorry if it's a dumb question.

tl;dr I need piston A to turn on before piston B, but Piston B turn off before piston A.