Kill the Lag. Do a Lag Fix
Galaxy S4 Lag Fix Makes it 10 Times Faster! - YouTube
1. Go to Settings/More/About Device and hit 'Build Number' 7 times.
This will open up the 'Developer Options' found under the 'More' tab.
Now with the Developer Options available your next step is to kill the Lag.
2. Go to Settings/More/Developer Options and look for the following:-
a. Window Animation Scale
b. Transition Animation Scale
c. Animator Duration Scale
For each of the above change the animation scale from '1x' to 'Off'.
Finally, load an App, any app will do and notice the immediate effect as apps open instantaneously.
If you want to take this further and kill the Lock Screen delay do the following:-
1. Settings/My Device/Lock Screen and tap on 'Unlock Effect' and change it from 'Light Effect' to 'None'.
2. Turn off the phone and turn it back on. At the Lock Screen swipe to open and notice this time it opens instantaneously.
Job done, visually you now have a much faster device.