
Everyone has an idea or a specific scene in mind. But that's what separates us from authors, they take the idea and give it substance. They think about how to get to that specific scene, they don't lose momentum just because they can't get to that specific scene fast enough. They think about what happens after that specific scene, how to tie it all together and then tie it all up.
If you really want to write a book, start watching videos and reading guides on how to actually get to where you want to get.
And I do recommend writing in English, writing in English will help improve your vocabulary. But if you find French more comfortable, then go for it!

Hello! Hobby author here!
If you ask me its good to start on some kind of plattform like ao3 or wattpad.
You dont have to start with a story that will have 10 chapters, you can also just write a one-shot or Story that is complete within 1 chapter!
I also write in english even though its not my mother tongue but you can write in french if u r more comfy in that! :p
If you write many chapters I'll just say:
Know where your story should start and where it should end.
Like this you will have a nice ending and won't be like one of many authors that don't have one ending at all or have a sloppy one.
Besides that:
Maybe read some stories if they should be fanfic and know what your preference is!
Is it a AU?
Is it fluff?
Is it smut?
Maybe even try a grammer app if u write in english so that it removes your spelling mistakes ^-^

I know that feeling so well but since I study movies and there you need to know the beginning and ending i thought
"Wouldnt this also work on my stories?" So i tried and its very smooth and nice to read ^^
Its also good to know how many chapters you want
A smooth 5? Maybe 10?
So you know how many words to put to get to the ending and how many chapters you need to fill to be happy with your own work!

I used to write fanfics, and I'd get the question about consistency all the time. Write every single day. Even if you only write 20 words. That's a day of writing. Another thing, is that I would not release a chapter less than 1k words. For real authors 1k words a chapter isn't much, but when you're writing for fun then that's a goal. If you want to be published, you should probably set a higher goal than 1k a chapter.
But about guides. There are so many on YouTube. You can even watch people take you on a day of writing with them. There are a billion free resources to help you start and get to actually writing instead of just imagining.
I want ro be an author but I dont even know the first thing about writing novels or world building I have seen some instrgram author talking about a draft and u have to build à story
But hear me out I get inspired of just one scène or specific moment in my head I dont have à whole story u get me?
And I really dont know which direction to take
Also I dont know in which language I should write
I'm most comfortable in french I used to write a lot when I was a teen also my vocabulary is more complex in this language,
But most of the books I read are in English so now I think in English or most of my thoughts
Tho one thing I'm sure of is not writing to in my mother tong that would be cringe and weird
It's still hard to chose