Why is my Galaxy Ace sooooo slow?

[AC Question]

Phone is slow, typed letters doesn't immediately show on the screen, screen freezes all the time and RAM is high. Just have the apps that I need like fb, youtube and messenger. My brother (who is the previous owner), said that it has already been rooted.

Help please. Thanks!

 

[Trashmob]

Because you have to close the apps frequently, and root does ruin the phone in my opinion... Galaxy Ace is a slow phone even if you didn't touch anything