Replacement screen flashes and goes black if I open apps

I bought a screen to replace my cracked one about 2 months ago from an Indian shop (the new screen is not a genuine apple screen) . After a few days the new screen started flashing and has lines accross it, it varies in severity. Now over the last week or so the screen goes black if I open apps, it slowly fades to black and I either have to wait 20 minutes for it to work again or I have to press the home and the lock button to restart it. When it fades to black it stops working completely, I can't still take screenshots or hear sounds. It's mostly happening if I open Instagram or 9gag but in the last day or so it happens if I open my camera or view my photos for more than 5 minutes. What is going on here? My phone worked perfectly before getting the new screen.