Question:

I see some leftover images from the last screen.

Answe:

Because of how the AMOLED display works, showing the same image for too long might cause something called "Image Sticking." This means you'll see faint pictures left behind on the screen. Don't worry; this isn't broken! It won't hurt your phone's life or performance.

To avoid seeing these leftovers, try not to leave one picture on the screen for too long. Turn off your screen when you're not using it. You can even make your screen go off by itself after a certain amount of time. To do this, go to Settings > Display > Screen timeout and choose how long you want your screen to stay on. Also, let your screen change its brightness by itself. Just go to Settings > Display and turn on "Adaptive brightness."