You do not know de way.
You fellow person cannot understand the right direction.
You, the subject of whatever person or thing I am referring to, is unable to comprehend and learn the correct direction and passageway.
You, the word which is used in 2nd person when referring to someone other than yourself, is referring to a certain subject but is unknown if whether they are a person, animal, object, or being, is incapable of comprehending and understanding the correct route, a way or course taken in getting from a starting point to a destination.