I dropped my iPhone xs max and it cracked but top half of the screen wont respond while the bottom half works. There are two possible ways you can fix it yourself or get through the problem. Bring down the screen with swipe down. Also you can open your phone and check the internal if your the screen cable attachment is all connect because if one attachment is loose or unattached certain part of the screen will be unresponsive. If these still not work the i recommend getting your phone fixed because your lcd or oled part might be damaged or it might be the display censor is damaged