What does the phrase ni hen hao war mean in Chinese?

The closest to "ni hen hao war" is 你很好玩 (Nǐ hěn hǎo wán) which means "You are very fun to play with".

玩 (wán) can also be said as 玩兒 (wa'r), which basically means the same thing (to play). It is just that the former is used more commonly while the latter is usually only used in Northern provinces (like Beijing) in China.