Use Server Reference Guide and QlikTech's Trianing Team has some material as well. And I strongly recommend you to work on Publisher & Server. Probably get a Temp Test license and play with it.
Sorry I mean the QlikTech's Server Training. Which is expensive in my opinion! However, please check ther Server Reference Guide which is pretty good. I have read it myself and found it extemely useful. Sounds boring but helps!
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