18-Year Old Apple Tree Struggles to Grow

I planted this tree in my grandma and grandpa’s yard in Garden City, MO from an apple I was eating that day. It’s about eighteen years old in this picture, which is very old for a tree this small. It has been ran over several times I think. It must have a large root system though for being so old. I’m not sure. You may or may not be able to see the pond in the background just beyond the fence. Behind the photographer is a barn they called Erich’s barn because it was the middle-sized barn and I am the middle child of the three boys.