hi am using a galaxy s4 and it won't let me move or copy an app or any file to my sd card, can anyone help?

Try downloading this free app called DU Speed Booster. This app not only allows you to transfer data from your phone to a memory card , but it also cleans out trash your phone has and has antivirus scans to protect your phone . It also signals you to let you know if you have too many back round apps running and boosts your phone if it's running slow . Also , make sure you access the Google app to back up memory as well -it syncs photos and contacts . Hope it works for you -post if this helped . Good luck