Have you just cleared the cache on your phone settings or have you tried wiping the system cache partition? If not try this:
1. Turn off your Galaxy S6.
2. Press and hold Power, Volume Up and the Home button
3. You'll see a blue screen with the Android on it, then you'll be taken to the recovery menu.
4. Use the volume buttons to scroll and highlight Wipe Cache Partition. Press Power to confirm.
5. You'll see a message in yellow at the bottom of the screen when the process is complete.
6. Highlight Reboot System Now and press Power to confirm.
7. Your Galaxy S6 will reboot and recompile all of your apps. It might take a little while to re-cache them all, but once it is done you should have a Galaxy S6 running as smooth as can be.