Re: how to clear up my memory
If you're talking about RAM (that's memory), you don't want to in Android. Unused RAM is wasted RAM. (Apps that claim to "free RAM" are written by people who think that Android works like Windows. In reality, it works just about opposite from the way Windows works. "Freeing RAM" slows the phone and wastes battery.)
If you're talking about storage (that's the equivalent to a hard drive in a computer), you delete files (apps, videos, anything) to clear up user (data partition) storage and you clear system cache to clear the cache partition.