i want to separete my photo to a layers. For example i want to have part of the picture in b/w and part leave as it was taken, so mi need layers. How can I do this?

Go buy Scott Kelby's book Photoshop CS for the Digital Photographer. It describes how to do it. From memory, it involves desaturating one layer, then using the brush tool to "paint back in" the color. Another way to do it is create a selection of the area you want to leave in color, then invert the selection, then desaturate the selection. That's sort of a quick and dirty method, though.

Here's an example, of where I left the shoes yellow, but made the rest black and white.