Huawei Y9 - Avoid task killers

It is best to avoid task killers such as Advanced Task Killer. Android is designed to automatically pre-load certain applications, even if you don’t load them yourself. If it starts to run low on memory, it will smartly unload the oldest running apps automatically.

Manually killing tasks will only mean they get loaded in memory again. Task killers can make the phone slow, laggy, or drain battery life more quickly.