How can I access my files on Galaxy J1 Ace? (restore "My Files" icon) At the moment, I can only access the files stored on my phone from the PC. I can access some music through players and pictures through gallery, but any other files that are there are hidden. Reading the manual, I realized this would normally be accessed through "My Files" - only... I don't have that icon anywhere. If it was there initially, I must have accidentally deleted it during the very first couple of minutes of having the phone and getting used to it. I hope such a thing is not irreversible? If I download something from the web, the download icon will show and then I am redirected to My Files, so they do exist, only the icon has gone and I don't know how to restore it or how else I can access the files without having to newly download something each time.
Did you try a third-party app? Some phones appears to have no file manager/explorer at all. 
To achieve this just install a third-party file explorer and you're done or if you think your phone had it before, you'll need to factory reset it then the icon will be back.

I'd recommend you to download ES Explorer but there are many other similar apps in the Google Play store.