Sm-g955u is laggy, charging poorly...reset phone?

[Elytherial]

I just need to know if I should do a factory reset and it so, suggestions on how to do a thorough back up first

 

[webworkings]

Quickest and most thorough, connect the phone to a computer via USB cord and copy all your files over to an empty folder on the computer. Then, after you do the reset you can copy them back to the phone.

NOTE: You can't do that with the apps.