My 4s automatically minimize the app that i'm using..

Greetings apple users, i wanted to share some of my experience in my device which i guess for me is very annoying. I would like to share, i don't know if you guys encounter this; sometimes when i was using some of my apps like Facebook or even play games, it will automatically minimized and you need to start all over again like opening the app again.. I already done basic troubleshooting steps like restart my phone, remove the app then reinstall it, clear some options(clear history, cookies, cache) and still its doing the same thing.. Is there any ways that you guys can help me? Don't worry i'm not mad haha i know there is no perfect product or software.. If you can help me thanks a lot and if you cant still thanks.. I'm just sharing this so that you guys will be aware of this. Have a nice day!