Insufficient storage on iPhone 5s after deleting photos and apps

I've almost cleared out my phone, an iPhone 5S (Old, I know- I'm getting there) of photos and extra applications, but for some reason, I simply CANNOT get any more space on my device. If anything, it went from about half a GB available to 11.8 MB as of now AFTER everything was deleted. I did note an increase in the size of the Other bar in Storage. I THINK System now shows a greater size. How do I proceed? I need to have more storage to make sure I can backup WhatsApp data so I do not lose some important information. Cannot use iCloud, apparently, since the backup wouldn't proceed despite it being half-empty.

[Re-Titled by Moderator]