Need memory on iPhone back

I have an iPhone 6 and it says I have 40 mb of memory out of 16 gb but the memory on my phone isn't adding up. I have deleted apps messages pictures and it remains the same or even shrinks! How can I get the memory I actually have back?

First of all, the IOS take up a bit. You can check on your phone under Storage and see just how much. And see what programs are hogs, that you clean out, our park offline. Get rid of extra things you have stored in Dropbox, Google Drive, and similar places. Save your pictures in clouds or drag them into files on your computer. If you saved a bunch of articles/recipes from newspapers, to be read later, then email them to your computer, and remove them from the Saved section. Once you have scrubbed all this, you are ready for the next step. Download Dr. Cleaner ( free, safe - Trend Micro) and run SEVERAL passes of it. This will clean out all the bits, fragments, and artifacts that are cluttering your phone. You should be ASTOUNDED at what is removes! We were. This will help keep your phones lean and mean We have used it on 2 iPhone 6 16M phones, for about a year - very pleased with what it does.

Get an android and expand your memory.

Plug it into iTunes,
back it up and restore it
if that doesn't work just restore it as new