If your looking to improve the speed and performance of your Sony Xperia Z3, then it may be worth closing some of the mobile phone applications running in the background. Simply follow the steps below to close these apps.
1. On the Sony Xperia Z3 home screen, select the multitasking button (this is the boxed icon on the right hand side)
2. Select and drag the application you wish to close to the left or right, alternatively, you can select and hold the chosen app then hit delete/remove from list.