I rent an apartment in the building on the first floor. 18 months ago
pipe burst in my apartment and flooded with 6 inches of water. At that
time landlord
replaced carpet and paid for cleaning and drying my belongings.
Now it happens again in apartment above and again I got 5 inches of
water and damage of my belongings. Now he refuses to replace damaged
carpet and pay for other service.

What would be the right response?

Write him a letter detailing the damage and what you want done. 
Include in the letter that you expect to hear from him by a certain
date and that if you haven't you will be filing a lawsuit.  Contact a
lawyer first, but you may be legally allowed to pay for the repairs
yourself if the landlord doesn't within a reasonable time and then
withold rent until you have witheld enough rent to cover all of your
costs.

Read your lease.  What does it say about situations like this?  What
you need is renter's insurance.  Just like homeowner's insurance but
it protects you as a renter.  If the landlord refuses to pay you can
take him to small claims court.