Q: How can I delete several photos from my iphone but keep them on icloud?

You can't because once you're using iCloud Photo Library that's how it, unfortunately, works -- delete the photo from one device and it's deleted from all devices.  That's how iCloud works because it's a syncing/mirroring service, i.e. it uploads the photos and videos to all of your devices -- originals are kept in iCloud, copies on your device.

You're most welcome!