How can I fix a glitchy screen?

My iPhone 5c was dropped about a month or so ago which left it with little black lines that gave it a look of an old messed up tv. Now, a couple days ago it randomly started glitching, the screen would go all over and I wouldn't be able to click on anything. (Kinda like the tv in the horror movie the Ring) but would go back to normal for a few if I wouldn't touch it. Now it's a black screen that becomes a light grey when a notification comes through and I have to push hard on the top part of the screen to be able to get any type of image