The difficulty of a language is relative to the person trying to learn it. In the case of the Chinese language, I have to say that it's a pretty difficult language to learn for several reasons.
As you can see, the Chinese language is pretty difficult to learn. I think that the main reason why it's so difficult is because it's just too different from anything we're used to.
Of course! Just like you might find it relatively easy to learn German (because it's similar to English in many ways), so do Korean, Japanese and other Eastern Asian people find it easier to learn Mandarin. If you have any knowledge of the forementioned languages, you might realize that learning Mandarin is much easier than you previously thought!
Additionally, learning a new language is always easier for younger people. The younger you start learning the language the better, which is why you should start right now!
Lastly, there are people with a natural talent for learning new languages. If you already know several languages, chances are that learning Mandarin won't be too difficult.