Well, English may seem easy, but I believe it is not. Actually, when I first started to study it, I thought it was very simple (as compared with French or German), but I soon discovered it was not the case. When I started to study it at a more advanced level, I soon found out that there are many exceptions to the rules (almost in all cases) and it is quite difficult to learn the grammar, especially. As for the vocabulary, here are the collocations, the phrasal verbs, idioms and this kind of stuff, which are also quite hard to study and to remember. Therefore, I believe English is indeed a difficult language.