how can i only delete photos from my mac but not my icloud and other devices

See a thread Cloud and Hard Drive - Apple Community

Keep your Mac up to date - Apple Support

When an iPhone and Mac are signed with same Apple ID and password on the same network and photos box is turned as on the photos will sync , if photos are deleted from iCloud.com they will get deleted from iPhone and Mac .

In Mac set up photo library and its preferences see the articles 

Set up and use iCloud Photos - Apple Supportsupport.apple.com › en-in

Change preferences in Photos on Mac - Apple Supportsupport.apple.com › en-in › guide › photos › mac

System Photo Library overview for Photos on Mac - Apple ...support.apple.com › guide › photos › mac

When photos are hundred percent synced , sign out Apple ID from an iPhone .

Sign out of iCloud on your iPhone, iPad, iPod touch, Apple TV ...support.apple.com › en-in

And sign in with new Apple ID and password that is created with you in the past .

Sign in with your Apple ID - Apple Supportsupport.apple.com › en-in

Then share photos from Mac to iPhone .

Subscribe to shared albums in Photos on Mac - Apple Supportsupport.apple.com › en-in › guide › photos › mac

 The Apple ID and password are totally different in iphone and mac if you delete photos from mac or icloud the photos will be not deleted from iPhone .

The invitation has to be accepted to receive photos ( has to be subscribed ).

Share iPhone photos with Shared Albums in iCloud - Apple ...support.apple.com › en-in › guide › iphone › ios

Your previous old photos are in primary icloud account and are not lost as they are saved on Mac .

Hence photos are in iPhone as well in Mac - this method was according to your original title - How do I delete photos from my iCloud account but leave them on my iMac and iPhone .

See the "How do I turn off iCloud Photos on only one device?" section of Get help with iCloud Photos - Apple Support and turn off iCloud Photos on your Mac and then delete the photos from it.

ShokoufehA wrote:

Thank you. I already turned off the photos from the icloud on my mac. But do i don't know how to delete from my mac only. Could you please advise on that as well?

Do you want to delete all photos summarily from your Mac and stop using the Photos.app on your Mac completely or remove only selected Photos?

• If you want to remove all photos from your Mac, quit Photos, then move the Photos Library from the Pictures folder to an external volume, to keep a copy of all your photos, just in case you regret the deletion. Then delete the Photos Library from the Pictures folder and empty the Trash. All photos will be gone from your Mac.
• If you want to delete just some photos from your Mac, make sure, iCloud Photos has really been disabled on your Mac, then open Photos and select the photos you want to delete. Enter the keyboard shortcut ⌘⌫ to move the selected photos to the recently Deleted album. Now empty recently Deleted. Do not let get Recently Deleted very full, Only trash up to 500 photos at a time, then delete then empty Recently Deleted immediately.

If you have iCloud Photos turned off on your Mac then any photo deletions that you do on the Mac will only delete on the Mac and will not sync with iCloud or other devices.