Here you go.. read this article. It is written by my esteemed colleague in detail. It has got all the information you need to learn about how reward system works
As for your query about your delegated steem power vanishing, that SP is delegated to you by Steem blockchain once you sign up. Since alot of people have joined the platform so your delegated SP has been taken away (everyone else's too) to accomodate new members. Once those members earn some SP of their own, their delegated SP will also be taken away. No need to worry about it :) i hope it helps. If you still have any questions, please feel free to ask
Thanks you very much for help @jbn