Replying to N00b question regarding android s5

so i just switched from iphone to an s5, I have struggled to find an easy way to transfer music. google play has been glitchy and not uploaded what i wanted, and what i did upload i am not sure if it's actually on my phone and not just on the manager. I dont want to be using data every time i want to play music. iv tried doubletwist didnt work very well. i finally just bluetoothed it to my phone but that takes forever.

what is the easiest, most simplistic way to transfer files? (photos/music/docs etc)

and if you have any tips for a new android user please let me know:)

thanks!