I am 157 cm and i weigh 50 kg is it too much?

Answer 1

Wikipedia discusses this in its article on Body Mass Index (BMI)

Your BMI is ( 50 / 1.57 ) / 1.57 = 20.28

This is at the lower end of the range considered normal, which is 18.5 - 24.9, so you are fine; if anything you could add a little weight.