Focusing problem in nikon d5000?

I use Nikon d5000 18-55mm AS-F. Some days ago i clean my lens and mirror slightly with only cotton. After clean i saw my picture is not good. Basically low light picture have so noise and blur.focus is not working.could you please help me what is the problem. And solution.

You'd be better off asking this question in your own language - your English is incomprehensible.

I would say you damaged your camera's mirror when you fiddled with it. This kind of work should be left only to a qualified repair person.So, I'd say, that's where you'll have to take it now to get it fixed.

The reflex mirror is not an ordinary mirror. You have found that out. It has special coatings that make it extremely difficult to clean if you don't know what you're doing. You will eventually make it more dirty than before you started cleaning it. The same goes with the focusing screen.

To see if it's indeed the mirror, set mode to Auto, ISO to Auto, AF on, white balance to Auto, and EV to 0. Go out and take a picture of a brightly colored car parked under the sun. If the picture comes out bad, have the camera checked at the authorized service center right away.