Q: Serious error with two sequential actions on iPhone 5,6 with iOS 7, 8

I bought iPhone last month. This is the first time i use iOS after many years using Android.

And i really got some disappointed with iOS. Because i saw a serious error with screen touch when do two sequential actions.

For examples:

1. When i view a picture on Facebook. Then i close the picture and do quickly for the next action. And the result is the next action does not working.

2. When you close a application and do quickly for the next action. For example: open a other application. The result is like above.

This error happens with any application on iOS 7,8 when do quickly two sequential actions

Please help to resolve this error.

Thank you!