My 2 questions are:
1) how long does it take for approval? (my case is straight forward)
2) Do they keep my passport until the descion is made?
I've just answered your questions in the other thread, but you didn't mention your passport there, so I'll just say something here too:
1) If you used priority processing and your case is straightforward, the visa should be approved within 15 working days of them opening your package.
2) Yes, they keep your passport, because they have to put the visa inside it

. No passport = no visa, and if you tried to ask them to give your passport back, your entire application would be withdrawn, you would lose the application fee and you wouldn't get a visa at all (you would have to reapply all over again).
However, if you paid for priority, then you should hopefully get your visa in the next couple of weeks anyway.