I have one side of my wall that has a tub surround at the bottom and i will soon have concrete board at the top. the other side of that corner has tile that has been partial removed with concrete behind it and some time of drywall or plaster at the top. here is a picture below. Im trying to figure out how to cover this up and make it look nice. Ive already tried to cut a piece of concrete board to put on the edge of the tub surround but every piece i cut breaks and crumbles cause its so small. im trying to get it level and even so i can put a corner bead on it. what do i do?