How to improve the functionality of the iPhone 4S?

I feel like it freezes too often and that it kicks me out of many apps etc. Advice? Suggestions? Anything? Be nice… I can't buy an iPhone 5 or 5S

Have you upgraded it to iOS 7, i think update is available for 4S. Do confirm & upgrade your OS it will resolve your issues

I would try restoring it to factory, maybe you have some bad app causing it. Also make sure you close all background apps, most just leave everything open and that consumes resources