My new racket

I just bought a new racket and I put Donic Sonex JP Gold on the forehand and i am not able to control my topspin and block properly. What should be done?

Give it a try for a week or so and then if it is still too fast buy a slower rubber.  Play slowly for a while to develop the feel and control of the rubber.

You can keep the other rubber till you have improved more and then try it again.