No, probably not, but that’s par for the course, and unless the book is non-fiction, it’s not really too important. Why? Because writing the book will show you what you need to learn. And gaining a new kind of knowledge is one of the best parts about starting a large writing project. It’s like moving to a new town; you can know the stats, the best rated restaurants, the ‘ten things you must not miss’, but until you live there and communicate with the people, you’ll never really know enough to speak accurately about the character of the place. It’s the same with novels or scripts. You have to write them (and discard many!) before you begin to understand the world you are building. You have to have those awkward first introductions and strange, misleading interactions where you walk away wishing you had said something else, or unsure about what was just communicated. Your characters are people that you are meeting, not just creating, and so you need to observe their behaviours, how they make you feel, what they actions/emotions they trigger and bring to the story. They are your new community. To really write authentically you must take your time getting to know them, to open yourself to your new surrounds by offering them the space and flexibility to develop. Like you would in any new society, so, no, of course you don’t know enough to write this book (that would be presumptuous) and that’s okay. You just have to know enough to want to spend some time there and have a general idea of what might happen when you do. Otherwise, you simply write it to know it.