fill screen problem

[minimignon]

While I was playing Jewels star, I touched underneath the game, right of the open apps icon, the 4 little arrows. I had the first option on and tried the second and then the third, wich is "fill standard screen". There came a black border around the game,wich I dont want but I cannot change it back. The 4 arrows show but dont react anymore. I uninstalled, wiped cache but when I download the game it comees with the border. Does anyone know how to change it?