iphone 6 iOS 8 : Is my multitasking broken or am I doing something wrong?

I just purchased an iPhone 6, with iOS 8. I am trying to get several things to work. This is my first iPhone, I am not familiar with how to use it.

The user manual says multitasking is achieved by double tapping the home button. When I double tap it, the opened app is "lowered" a little and about a third of the screen, from the top, becomes black. From when I understand, the current app and other opened apps should appear in that black area. But they don't. Am I doing something wrong?

Also, by clicking the home button, I only suspend the app, not close it completely, right?

Thank you

Double click the home button. Double tapping without clicking will do as you have observed.

Be sure to depress the home button twice.

The behavior of the double tap is to allow for easy reach of the top of the interface when using one hand.