My specs power (-4) , please suggest some effective measures to improve my eyesight from myopia.

Mostly technical: There are no measures using herbs or exercise to improve myopia. A level of -1.00 is fairly small and at your age is likely to increase but never to get too high. You should use contacts or eyeglasses for the moment and when old enough (usually about 23) you can consider lasik for a permanent cure.

Glasses or contacts: Most people would wear glasses or contact lenses. Other options include ortho-k (orthokeratology), where you use special contact lenses at night to reshape to cornea, so that contacts are less necessary during the day. Also refractive surgery, such as lasik, can give a permanent correction, but is using performed after age 18 to ensure that eye is fully grown.