When to use a complement? I recently said to a native Chinese speaker: "你跑步跑得很快“ ,and then asked him if that sentence was grammatically correct. He said he understood what I was saying, but that he would have said: ”你跑步很快“. 

I thought you had to use a complement in such a situation. Which is correct, and why?
你跑步跑得很快, grammarly correct and common.

你跑步很快 common but odd a little.

你跑得很快 grammarly correct and most common saying.