If you have Verizon Wireless you may need to activate HD Voice in your account. I had to do this with my phone so I could use the data during a phone call. https://www.verizonwireless.com/support/...-base-130983/
Depending on the android operating system you are on, you should be able to press and hold the home button to see all the windows that are open. then there should either be a "Clear All" or 3 horizontal bars that clears all of the open windows. You may have to swipe up or down to see this button. Hope this works for you.
Do a Google search for M215HGE-L21 REV.C2 which is the screen for your model. I mostly found suppliers where you had to order a minimum of 5 screens. You could always sell the ones you don't use. But for some reason I couldn't find them for sale on their own either, except for the used ones.