Is writing all about being creative and making things up?
Yes and no. It depends on the kind of writing you prefer to do. While fiction writing, certainly, has much to do with creating fictional worlds and stories, there are lots of other - equally valid - forms of writing that you can take on. Essay writing, copy writing and technical writing are just a few.
Is learning to speak English more difficult than learning any other foreign language?
Not at all. In fact, learning to speak English well is much easier than learning to speak most other languages. For instance, while most foreign languages rely heavily on knowledge of the gender of specific nouns, this distinction is almost completely irrelevant in the English language.
In what way does mastery of the English language help me in the real world?
Being able to speak, and write, English fluently and correctly can greatly enhance your ability to succeed in almost any arena. Regardless of what career path you choose, being able to communicate effectively is the cornerstone of success.