Currently using 41GB, I try to down grade my storage from 200 GB to 50 GB but the DONE button is not available to click. Please advise.
Okay, please the steps in https://support.apple.com/en-us/HT207594. If you still get stuck, I'd suggest giving AppleCare a call. You can find the number in AppleCare contact Information
I think you are referring to your iCloud Storage, is that correct?