See these article Get help with your iCloud Photo Library - Apple Support
If you want to remove photos and videos from all your iOS devices, your Mac, and iCloud.com, you can delete them in the Photos app.
When you delete a photo or video from your Photos app, it also deletes from your iCloud Photo Library and iCloud storage. You can recover your photos and videos from the Recently Deleted album for 30 days.
To delete an item from iCloud Photo Library, just delete it from your Photos library: while viewing the photos in a moment, select the item you want to delete and press Delete.
Deleted photos and videos aren’t immediately removed from your library; they’re placed in the Recently Deleted album, where they remain for the number of days shown, and then are deleted. You can remove the items immediately using the steps below. Once the items are removed permanently, they’re no longer available on any device that uses iCloud Photo Library.
- To immediately delete photos from the Recently Deleted album, click Recently Deleted under Albums in the sidebar.
- Select the items you want to delete and click Delete [number] items.
- Click OK.