Phone Storage Full/Cloud is safe ?

You should copy the photos from iCloud to your computer first, deleting them on your iPhone will also remove them from iCloud Photos.

Have a look at the steps mentioned in this article:

Archive or make copies of the information you store in iCloud - Apple Support

Nadine09 Said:

"Phone Storage Full/Cloud is safe ?: Hey my phone storage is full and I would ask when I delete my pictures on my phone. Are they pictures still in the cloud ?"

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Clearing Space on an iPhone:

Use my User Tip: How to Clear Space from your Mobile Device, and What to Clear - Apple Community