i know i spelled it wrong but i need help with the back palm with more than one card the don't stay and if i am lucky i can produce all of them at the same time not one at a time
Simple answer: Practice. Practice a lot.
You need to build more finger strength and coordination/dexterity to palm and produce multiple cards than to palm and produce just one card. Continuous, diligent, careful practice is really what you need, if you have learned the proper technique in the first place, .
Having said that, I have to ask this: Where did
you learn to back palm a single card in the first place?
BTW, Jeff Sheridan's card manipulation work has been available on video/DVD for years. Look for the "Jeff Sheridan: Genius at Work" set. Those of you whose conception of "street magic" comes from David Blaine really should check him out.