Never install the Google Photos app on an Apple device
Never install the Google Photos app on an Apple device, like an iPhone or an iPad. The app slurps up all your photos and videos, even though they were probably automatically backed up to iCloud already. Then, Google complains that you're out of Google cloud storage space, and services like Gmail stop working. (Well, they stop working exactly the way they should. For example, you may not be able to receive any more emails.) You can solve the problem by paying Google for more cloud storage space, but that's bullshit. There's no reason to pay them, because they had no legitimate reason to steal your data in the first place. Fuck that. Thankfully, there is an alternative. You can uninstall the app, then delete all of Google's copies of your media through the Google Photos website on another computer.
That's all a very technical way of saying the following: never install the Google Photos app on an Apple device. If you already installed it, uninstall it, then delete Google's copies of your photos and videos through the Google Photos website on another computer.
There may be a workaround. There may be some kind of button that instructs Google not to steal your shit and charge you for the privilege. If there is a solution, though, it must not be obvious, because practically everyone I know with an iPhone has faced this problem. Therefore, the easy solution is the best one: never, ever install the Google Photos app on an Apple device.