how sleeping helps to reduce stress?

Yes Sleeping is the best remedy for the stress. It removes the pressure of
your mind and makes your nerves relaxed. Its circulate the blood in your body and mind. and you feel fresh and energetic.

These tips from WebMD may help you reduce stress so you can sleep better at night. High stress levels can make sleeping more difficult. At the same time, getting a good night's sleep can help reduce the effects of stress. When we do not sleep long or well enough, our bodies do not get the full benefits. Thus, managing both sleep and stress is important in leaving.... weight loss Manchester

Google it :P

The brain gets to "defrag" as it were.

I understand that Einstein himself took regular naps.