Low Disk Space but already did everything

Google Drive (and iCloud) do not add any storage to your iPhone (or Android phone). They for offline storage only.

It is not possible to buy more storage for an iPhone; it will never have more than it did when you bought it. What you can buy is iCloud+ storage that is used for backing up and also for syncing to other devices. Here is an explanation→What's the difference between device storage and iCloud storage? - Apple Support

iCloud+ has 2 independent functions. iCloud backups, and iCloud sync. It’s confusing because they both have the same name prefix. But they have no connection with each other. Go to Settings/[your name]/iCloud. You will see a bunch of switches (with iOS 16 or later also tap Show All). When you turn on a switch that data type will sync to iCloud. If you do this on multiple devices that share an Apple ID the selected data will sync to all of those devices. 

You can also turn on iCloud Backups. This will back up your phone every night if the phone is plugged in, connected to Wi-Fi and locked.

But note that these are independent functions; anything that you sync by the first method will be excluded from the iCloud backups.

You get other benefits with iCloud+

• Hide my Email, which lets you access websites without giving away your primary email account (and also track who they sell your identity to)
• Private Relay, which is sort of a super VPN (at much lower cost than commercial VPN)
• Custom email domain, so you can create a personalized email address that forwards to your Apple ID email (such as jane@doe.com)