If ghosts can walk through walls, why don’t they fall through floors?

Well I don’t know, but I’ve seen my dads mother when I was like 6/7/8 years old, I was on the floor as the other rooms were occupied by my sister and eldest brother and me my mum and other older brother were sleeping on the living room floor, and, I saw a figure walk past the window, and threw, the front door, 🚪 it was a glass door, and she went through it, I’m 39 now, so 30 years ago this was, and she walked up to me and handed me a red apple from her basket, I think I took a bite but I saw things in that apple I don’t remember what, but I had a tear in my right eye, and my mum saw it, she lies when she says she didn’t, she was awake with me and saw the apple, and everything, the reason how knew it was my dads mom, is because she went up to him, and stroked him towards the fireplace