I'm going to advocate for the basic if unwieldly: plug in your phone to your computer and move files from one to the other that way? if you use a MAC this will be slightly more convoluted - Macs refuse to see Android devices as external drives - but in that case you should be able to install AirDroid - this is basically like a cloud account allowing you to upload files from the web (so, for example from a browser on your phone or a browser on your mac) into a place where you can easily retrieve them later fir use on your phone.

I haven't tried it yet but that's one of the solutions I have envisioned for similar issues.