I presume when you say "memory" you mean that the storage is full? "Memory" more commonly means RAM, so if you mean that your RAM usage is high then don't worry about that, it's the way it's supposed to be (and under no circumstances install a "ram cleaner" or any other crap of that sort).
For storage there's not much you can do. You can buy a microSD card and move media to that. You might be able to partially move some user-installed apps (if you can it will be via Settings > Apps, select the app and look for a move to sd button), but that is limited: not all apps support it, and it only moves a part of the app. You won't be able to format a card as internal storage because Samsung never supported that on their flagships. So it really comes down to uninstall apps you don't need, move media to SD, and if you get desperate try clearing some app caches (browsers can cache a lot of junk), but that's only a temporary fix.