I just tried to stop this loud whistling noise but unsuccessful. I could not get the diaphragm to come out.
HELP HELP HELP

Don't understand that. It is just a little piece of rubber. It easily comes out. Have you removed the plastic cap of the fill valve. You must hold the little lever of the fill valve up in order to twist and remove the cap.

Hi Ronny and Welcome to The Plumbing Page at AMHD.com. You're responding to a 7 year old dead thread. so I gave you one of your own. Please check the date before you post. Thanks

I could not get the diaphragm to come out.
Which fill valve do you have? Back to you, Tim