Help moving files from phone's internal to SD

Hello there, before i frustrate myself trying to understand this through google searches…

I have a Motorola Luge phone… which if i’ve read right, runs on an Operating system they call KitKat?

Anyway, i’ve given it a MicroSd card because i save alot of files and take alot of pictures.
The internal storage has gotten full once in the past and i somehow managed to find a way to transfer them with the file manager but i remember that process is a nightmare and also duplicated the folder the files were in (so now i have 2 snapchats, 2 cameras, 2 facebooks, 2 downloads, etc) and also completely destroyed the order the files were in there for. new images were in the back, older ones near the front and many just where ever they happened to land in the transfer.

Here i thought i set my phone to save to SD now but nope! the images and videos still were saving to internal and now it’s full again and cause my phone to lag (and zoom in on it’s background image every time it hiccups at all for some reason)

I’d like to find a way to more easily transfer these files, and maybe clean up the folder issues on the phone so that there’s only one of each again… and then try and set it so photos and videos save to the SD.

Anyone know of any apps that are helpful for doing this that won’t corrupt/lose the files?
Or anyone have a clear step by step list of how to transfer the files if not the first question?

Thanks a ton!