How to Free Up Memory Using Device Care 

If your device is sluggish or your apps aren’t functioning correctly, you can free up memory on your device by closing apps running in the background.

How to Clear App Cache on the Galaxy S9 Or S9+

You can clear an app’s cache if it’s giving you trouble, etc. Clearing the cache on an app is like doing so in a web browser. It’s good to do this if the cache is full or has outdated information messing with the app’s performance. 

How to Clear the System Cache on the Galaxy S9 Using Recovery Mode

Android devices that shipped with Android 6.0 or older download and store system updates in the system cache. Then, it applies them when you reboot. Phones that shipped with Android 7.0 and later have a more efficient system. It’s a good idea to clear the system cache after updating your smartphone to get rid of outdated files and data.