I replaced my screen but the screen is black while underneath it works

It could be a bad screen, an improper installation or damage to the logic board.

Start by installing the original, presumably cracked screen, to see if everything still works okay. If it does, then you have a defective replacement screen. If it doesn’t, then you may have damaged the logic board. Did you disconnect the battery prior to removing and installing the screen? Forgetting to do so can damage the backlight filter (your’s appears to work fine though) or, less commonly, the LCD driver. Also check the condition of the connectors as they are easily damaged during a repair. While you’re at it, take a close look at the small components surrounding the connectors as sometimes they can become dislodged when prying off the flex.