That was what I was thinking of, when I asked for the Other storage. There's a part in your storage that shows up in an orange colour, as far as I remember. It's called "Other". (I didn't ask for the rest of the storage, just for that one.)
When Other takes too much space on your device, it could also mean that there are corrupted files somewhere.
Restoring the iPhone was the right way to get rid of them. I'm glad you found the solution without assistance.