How come they dont use 키가? Is it only used when talking about people's heights?
You use 그만큼 in a sentence if you are showing how big or how much something is.
Ya. It seems like someone is pointing at a tree and saying "the tree is as tall as itself." Kind of pointless, but I guess we haven't learned comparison words yet.
이 the object is close to us 그 The object is close to you, but far from me 저 The object is far from we both