trying to delete photos on my Mac but keep in icloud

What are you trying to do? Partial deletion on the Mac or complete? Temporary or permanent?

Are you trying to sever the connection between Photos on the Mac and Photos in iCloud entirely? Disable iCloud Photos in Photos > Settings > iCloud. Now the deletions or additions you make on the Mac won't be made in iCloud and vice versa. If you reconnect them later, they will be merged.

If you are trying to create only a partial asymmetry between the Mac version of the library and the cloud version of the library but allow future additions or deletions to be synced, there is no way to do that. iCloud Photos is a full-sync service.

Open gallery, and then above in the bar click preferences and turn off iCloud sync

You have to turn off gallery in iCloud and then you can delete on the pc and the photos still will be in iCloud.