Double vision screen, not wallpaper

So, my mom gave me this phone after she stepped on it (it had service and I didn't have a phone, so why not?) She said it had a few problems with the upper left corner of the screen not working, so I thought it wouldn't be a problem, just the sensor being broken, fixable. But then my screen started to duplicate itself so that there's a second image of the same screen on my phone. Is this because of the broken sensor, or the fact that it was stepped on? How can I fix this?