Storage

Try using iTunes to check how much storage is actually on the device -- How to check the storage on your iPhone, iPad, and iPod touch - Apple Support.

Example....

1. Open iTunes on your computer.
2. Connect your device to your computer.
3. In iTunes, select your device. You'll see a bar that shows how much storage your iOS content uses, divided by content type.
4. Move your mouse over a content type, like Other or Apps, to find more information:

iCloud storage does not increase why you have on iPhone, to make space you need to delete stuff you don't need.

iCloud storage is for your backups and syncing to all your devices.