My difficulty has always been in the compression of the language.
A very simple example of this is in the phrase 中美. By itself it quite literally means central beauty, center of the beauty, in the middle of beauty, but in practice it actually means China and America. This is because this is a compressed form of 中国美国, but the 国 has been omitted to shorten it.
In Mandarin this happens constantly, characters seem to just disappear, and if you don’t already understand how this compression works and it is almost never taught in school or in books, then you will be left confused.