but sometime when ram is almost eat up, application is so laggyRemember that Android prefers to keep RAM mostly full, unlike Windows. Empty RAM is useless RAM with Android. Just let the system take care of RAM management, and don't use any "RAM booster" or "RAM cleaner" apps.
i mean it's is used by many background service or application we dont see, so i want to know how to optimize ram to make phone run smootherWhat do you mean by "eating RAM"?
You have no control over the amount of memory an app uses while it is running.
If you are running out of storage space, that is a different question.
It may have to do more with what specific apps are running. Do you have any RAM booster apps installed? Those can ironically slow the phone down.
Does the stock cleaner app have any automatic settings? If so, turn them off, and only use it manually (if at all).
The next time it's lagging, go to the Settings menu that shows you all of the running apps, and show us a screenshot. That menu's location can be in different places on different phones, so look around for it.