how do I close open windows on samsung galaxy 10.2 tablet?

[AC Question]

Tablet says "cant open wondow until you close some".

 

[Janit Lodha]

Try to close the apps which are running in the background by pressing the recent option in your tab, that might do the work

 

[Rukbat]

Tap an open window, so it's the foreground window. Long-press the back button. It not only closes the window, it kills the app. (Properly written Android apps save their data as they go.)