The Samsung Galaxy Grand Duos has some issues with the image gallery app (version 4.2.2 - I9082XXUBMK5), that wrongly shows to use more space than it physically has (8GB).
The notification "Storage space running out - Some system functions may not work" is often shown. When this issue happens the phone is unusable, and it takes ages to reach the screen with the "Clear data" button for the Gallery app, that's why I made this shortcut, that brings you directly where needed.
Unfortunately this is just a temporary workaround, it won't fix the bug in the Gallery app, it will simply bring you to the button that permits you to normally use your phone until the next storage space notification.
On many Samsung devices you can also free up other storage space by dialing *#9900#, a hidden menu will show up and you'll be able to remove log files clicking on "Delete dumpstate/logcat".