Welcome to the Apple Support Communities. I understand your iCloud Backup has been taking some time to complete.
Has the restore made any progress since you made your post? While there's not a list of the data that still needs to be restored, you can double-check your apps to see if your restored content is there yet; for example, checking Contacts, Photos, or any other apps that were backed up to iCloud.
It should be safe to tap "Stop Restoring iPhone" and then starting the process over, but there are a few things to consider first that might help If iCloud Backup couldn’t be completed or you can’t restore :
In your screenshot, I see you're connected to Wi-Fi and a charger. Has your device consistently been on Wi-Fi and the charger during the restore process? You'll also want to keep this in mind, as it's possible that the restore is still processing:If the restore process takes a long time to finish
Stay connected to a reliable Wi-Fi network and a functional power source until the process finishes. The time it takes to restore from a backup depends on the size of your backup and the speed of your Wi-Fi network.
I hope this helps you.If a message says that your restore is incomplete or some items won't restore
These messages mean that you disconnected from Wi-Fi during the restore process or that some of your apps or content couldn't be restored. Here are some possible causes and what you can do about each:
If a message says something like, "Restoring 350 of 1200 items," then your photos are probably still being restored. Keep your device connected to a reliable Wi-Fi network and a power outlet so that the process can finish.
Take care.