Sanskrit is the oldest language in the world and Lithuanian is related to Sanscrit.

I think "Body Language" is the oldest Language. :)

Chinese，5000 years old

Your question is poorly asked. I say "Written Chinese because it has the longest continuous history and the rest are dead languages." This reminded me of this question posed to a Filipino beauty contestant, "How many islands are there in the Philippines?" Her answer? "Are you talking about high tide or low tide?"

I have read books stating Sumerian was first.