I suggest you: 1. Click the nearest application key in the lower left corner of the screen (that is, the touch key on the left side of the only physical key on the screen)-click the circle icon in the lower left corner-click the end icon on the right side of the application or end all to close the background running program. 2. Uninstall the self-installed application. 3. Clear the Internet cache of the mobile phone: browser-menu key (three dot icons in the upper right corner)-settings-privacy security-privacy-delete personal data. 4. Clear the recorded incoming calls, text messages, etc.