I found my FA 35mm f/2.0 autofocused much faster than my 50mm, even though the 50mm was a stop faster aperture-wise. I shoot Canon now and my 85mm f/1.8 is significantly faster in autofocusing than any of my Pentax gear.
I think you should just stick with the kit lens for awhile and get used to it (and read up on some photography basics). To answer your 18-55mm question, that lens can be set to any focal length between 18mm and 55mm (inclusive). 18mm gives you a much wider "Field of View" than 55mm (I hate when people say 55mm is good for getting up close, you can get just as close with 18mm!)
By the questions you're asking, I don't think you are ready by be buying any prime lenses. So you have the kit lens? I'm confused..........Do you know what "focal length" is? Aperture? F-stop? Shutter speed? Learn these basics BEFORE buying any more gear (except for books, books are good to learn from
)