I have done this in the past month. But I can not do it now. I have tried a dozen times and when I move or copy to folder and then hit Paste here, nothing happens. I just did it on my wife's S5 with no problems so I know I am doing it right. Crazy.
Welcome to Android Central! Are you using MyFiles, or some other file manager? Have you tried moving the files via your computer's file browser after connecting with USB?
Try booting into Safe Mode, which prevents all 3rd party apps from starting up. If you can successfully move files in Safe Mode, then there is probably some app you installed that was interfering with the file transfer. Instructions for Safe Mode are at the bottom of that same link I posted before: Reset: Samsung Galaxy S 5 | T-Mobile Support
I would venture a guess that the issue you're having is due to either a glitchy device, or a problem with Samsung's interface. It probably isn't Android itself. If you got a Nexus 5 or Nexus 6, which isn't burdened by lots of manufacturer modifications or bloatware, you'd be less likely to encounter these kinds of issues. There are probably still plenty of options for you to switch back to iPhone, but hopefully someone here can continue helping you.
Did not work. But it did work before. The only thing I can think of is that I put a memory card in it. Heard about issues with them. That is BS to because it is made for one.