Question

water stops the fire but it is made by oxygen and hydrogen molecules which help in fire .how ?

Answer 1

As we know that water is a compound made from oxygen and hydrogen. So during a combustion process of hydrogen, we observe that the hydrogen atoms are oxidised while the oxygen atoms are reduced.
And thus the product of this reaction is water.
And also the bonds formed in a water molecule are stable so it can not react further. This is the reason why water could not combust or why water extingushes fire.

Hope my answer will help you.