Bestival said:
As to whether Chinese is difficult to learn, it depends on what background you come from. English speaker tend to find it difficult as there is no alphabet in Chinese - its a completely different writing system. Japanese/Korean speakers tend to have an easier time as Japanese evolved from Chinese, similar to how many European languages evolved from Latin.
Ok, I don't know where you got the idea that Korean and Japanese are Sinitic languages, because they most certainly are not. While both Korean and Japanese have borrowed a lot from the languages of China, including Han characters and substantial amounts of vocabularly, they are not actually related to any of the Sino-Tibetan languages.
Current linguistic thought is that they're isolates, but that they may be part of the Altaic group of languages, which would make them very distantly related to Mongolian, and Turkish. This notion is controversial as it depends on a small number of basic historical cognates.
Just because a language shares vocabulary and a writing system doesn't mean they're related. Indonesian uses the Latin alphabet, but isn't related to any of the languages of Europe that use it. Similarly, English borrowed large amounts of vocabulary from Latin and Greek, but is only very, very distantly related to it, while it's very closely related to Dutch and Low German, in spite of surface appearances.