Duplicate photos on Macbook, iPhone and iCloud

OK< this is driving me insane. I manually deleted all the duplicate photos on my iPhone, only to discover that they were repopulated either from iCloud or Photos on my Mac. I watched this, aghast after hours of carefully selecting and deleting the duplicates, there they were busily being repopulated on my iPhone.

Can anyone explain how this works. If I delete from either Photos on Mac, or from iPhone or from iCloud - all have the same photos and the same duplicates. Which one is the Master one so if I delete duplicates from that particular one, it wont repopulate the others again.

Sometimes Apple you seem to forget we arent all tech wizards.

Can someone please explain how I can delete all (the same) duplicates from iMac, iPhone and iCloud