Doesn't seem to be working

Hello,

just installed it and tried to find some more information but failed.

So I've created on basic page which is a bit longer and should act as one page with parallax scrolling.
Then I used the

.main-container

as Valid jQuery selector and put this into my css:

div.main-container {
	background-image: url("/sites/all/themes/bootstrap_barrio/img/bg.jpg");
	overflow:hidden;
	/* background-attachment: fixed; */
}

If I uncomment the fixed, the img stays where it is and the content scrolls.
If I comment it out, the img scrolls at the same pace as the rest.

Then I added another jQuery selector like: .content and gave it a different speed and to test it a background image as well.

But I can't see any parallax effect on my site.

jQuery seems to be working fine.
Any idea how I can get that working?