Can't get out of game apps on a RCA Galileo Pro Tablet

Have a RCA Glaileo Pro. In certain game apps I cannot exit the game unless I turn off the tablet. Also grandson dropped it - there is a small crack in the upper left corner. With some games I have to turn the screen for the lower section to work. This does not help however when trying to get out of the app.

Thank you for your help.

AC