there are several ways to save your mobile：
1.Get a new iphone.This is the most extreme and the most convenient, and of course it is the least economical method. After all, a new phone is worth a lot of money.
Apple once made a statement which mentioned for the iPhone, its design life cycle for three years, for the iPhone 6 or earlier for the apple iPhone, now has more than its design life cycle, and continue to struggle in the old iPhone, or directly in a latest mobile phone as well.
2.Don't upgrade your system
This iPhone users, mainly for the apple before the iOS version 11.2, the processor performance of iPhone 7 no limits, only after the update iOS 11.2 to the iPhone 7 joined the frequency limit of models. So if you are using iPhone 7, and haven't upgrade iOS 11.2, then shut off all the options about system updates, and now the iOS 11 is filled with all kinds of bugs, use experience also not so good, stay in 7 instead of the old version of the iPhone you have the best experience.
3.Protect the battery
For iPhone 7 users who have upgraded iOS 11.2, it's time to pay attention to the battery's maintenance, after all, the main reason is the attenuation of the battery capacity. Lithium battery is the most taboo of excessive discharge and recharge, it does not have a traditional battery memory effect, so in mobile phone display after a full charge, disconnected use directly, and don't put your battery use to the limit.
4. Change the battery
This is mainly aimed at iPhone 6S users, without replacement of the battery's iPhone 6S, and its battery has been decaying a lot. Through the actual testing of many users, the battery replacement can effectively restore the performance of the iPhone 6S. It's obviously cheaper to replace a new battery than a new one, and it's better to spend that money on the iPhone 6S for a year, which is better than buying or selling.