Problems apps synching with iCloud and memory running out
The problem is the local storage on the phone. The middle picture showing device backups isn't a problem - you have plenty of space in the cloud.

If you can't figure out how to prune what's app - you can try their support and/or deleting the app and letting the storage stabilize over a day.

Once you know how much free space of the 16 GB is available without over half being taken by WhatsApp - you can then document that and re-download that one app.



Things won't work well until you free up a GB of space and it looks like WhatsApp is the only possible solution to your current jam.