WHY DOES MY IPHONE DO THIS?

WHY DOES MY IPHONE DO THIS?!

Added (1). I'm so annoyed and confused!
i bought an iphone 4s 8gb two days ago and it was fine, i downloaded loads of apps and i was told i had no storage
fair enough, i thought, so i deleted at least half and now i only have about 9 apps from the app store.
i went on the spotify app to remove songs and lost another 500 megabytes! I deleted it because it took up 1.3 gb and didn't get any memory back!
i shouldnt have to wipe my phone just for some memory, so is there some settings i need to change?

Try clearing the cache memory. Uninstall/reinstall apps you wouldn't lose data from, like Facebook/Instagram