Joining creative writing classes is a great idea! I've also noticed that publishers specifically targeting new authors offer such workshops. That could also be very interesting.
It's also not just about "why" you write, but also "for whom" - you should always have a specific target group in mind. This is important for all areas in the book.
And as is said here - writing a book is a lot of hard work and usually takes a long time. Professional help is usually indispensable..