Android：如何在后台管理我的应用程序

I have this problem: my app android has a problems when it comes in background. When I press back it closes but when I re-click on it it doesn't work (button doesn't working) and when I close my app using home or an other app, if I re-click on it, it works but if I don't use it, after a little time it has been forced to stop. Why? How can I manage this problem? Thank you for allI have this problem: my app android has a probl