@kimoTaher: For clarity, are you wanting to prevent your phone from going idle while using it, and while accessing applications? If so, please head to Settings > Advanced Features > Motions and Gestures > Keep Screen On While Viewing > On. Also, head to Settings > Display > Screen Timeout, and increase the time it takes for the screen to automatically go into idle mode.
@kimoTaher: Apologies. Please swipe up from your Home Screen to access your App Drawer > Tap the cog symbol to access Settings, then head to Advanced Features > Motions and Gestures > Keep Screen On While Viewing > On. I hope this helps.