The decocker is working for you. It is supposed to bring the hammer to half cock.
At that time, you may fire double-action (DA) by simply pulling the trigger. It will also fire DA if the hammer is all the way down, but the pull is substantially harder as it gets started.
For defensive CCW & OC, I carry my decocker CZs (PCR/P-01/SP-01) chamber loaded with the hammer at half-cock. This give me a point and click interface with no possibility that I might pull the trigger and not fire the shot.