Want to delete photos to make space but when I do they’re deleted from iCloud too

iCloud is a syncing service, not an archiving service. It will keep all devices logged into the same iCloud account matching each other. So anything you add to a device will be copied to all other devices on the same iCloud account, and any deletions or edits made on a device will be duplicated on all other devices. What you need is an archiving service. Here are a few:

• Transfer your photos to your computer via USB cable
• Sync to Google Photos
• Sync to some other photo archiving service such as Shutterfly
• Sync to Dropbox
• Sync to box.com
• Sync to Microsoft OneDrive
• Sync to Amazon Photos
• back up to Livedrive
• Backup to any other backup or archiving service

That's the expected behavior.