in Chinese, why= wei shen me(為什麼)
the word 誰加 makes no sense to me. It is not officially a word. It only means "Who" by the indication of 誰。 As to 加, in this case, it is only an interjection at the end of the sentence used by some people in certain region of China. Some kinda interjection word in a dialect which I am not quite familiar with.