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..
When I envision my readers, I don't have a unified group in mind. I think it's similar to those who are interested in cryptocurrencies. They are people of different nationalities, different ages, with very different lifestyles and professions. All of them are certainly interested in the future and new technologies. There are also no children and probably relatively few old people. I think that would also coincide with the target group I have in mind for my book.