I'm only 9 and I started writing a few books, but I didn't even finish them all. I don't know if I should keep writing different books, or focus on one. I sometimes find old books of mine that aren't finished and I don't even know what they are about. I need a quick idea on how to fix this...
Welcome to the Writing Stack, Alayna.
When you write, it's usually more effective to focus on one project at a time
You've already noticed that you can't always remember what you were planning with previous projects. When you put a story down for awhile, it can begin to fade from your memory. So if you want to write a story, it's better to keep at it until you've at least finished a "draft".
(A draft is a version of a story or other piece of writing. Some writers will rewrite the same story several times before calling it really finished, creating several drafts. Even if you don't do that, you will still probably want to go back and fix spelling and grammar, and rephrase things so they're easier to understand.)
Working on just one project doesn't mean you have to finish every story you start - because sometimes you will get partway in and realize you don't really want to write that story after all.
If you do have to put up a story and not work on it for awhile, it's good to write notes to yourself about what ending you have in mind, or things characters are going to say or do, or what is going to happen next. That way, when you come back to the story later, you'll have a better idea what was happening.
In fact, I myself often write notes about things I want to put into a story, even if I'm working on it every day. I don't feel like I have to use every interesting line or every surprising event I think of - but I at least I remember that I was thinking about it, because it's right there in my notes.
After you've finished a draft, then you can let a project rest
A useful trick is to put a finished draft away for a little while, a week or a month or so, and then come back and read it again. It's okay to work on writing something else in the meantime. When you come back to a piece of writing you haven't worked on for awhile, you will often see mistakes that you couldn't see when you were looking at it every day and knew exactly what you were thinking about. Or you'll notice that you didn't explain things very well, and a reader who doesn't know exactly what you were thinking when you were writing won't understand. Now that you can see some of those problems, you can rewrite the places that need to be fixed, and the story will be better.
But first, focus on one project and write it to the end, and it will help you become a more confident writer.
I do not want to dissuade you from writing a book, no matter what your age is. However, this forum is designed to help the writer who has already selected an idea and is now looking for advice on achieving a given effect. This might be the design of characters, the structuring of scenes, the specifics of dialogue, or the use of point of view. Not what to write, but how to go about writing. The possible topics are endless.
Rather than dumping paragraphs of technique and process on you, let me suggest three practical things that you can do at any age.
First, start small. Write a short story that focuses in on a single topic; expresses a narrow, constrained notion; and can be written in a limited amount of time. Do not worry overly much about quality. Get the words down, finish the story, and celebrate. You now have something that you can revise, something that you can show others, something that you can get feedback on (even if it is only from your future self). Take it out after enough time has passed to make a re-reading fresh and untainted by the memories of what you thought that you wrote. You may well find that the story on the page is only a shadow of the story that was in your head.
Second, write every day, if possible. Even if it is only for 20 minutes. It might be an outline of what you want to say in your writing. It might be (what you hope will be) finished prose. It might be the revision of a single paragraph. The goal here is to develop the habit of writing, no matter what the distractions are, no matter how you feel, no matter whatever.
Third, invest in technique. Spelling, grammar, story structure, and punctuation are all things that you can spend a few minutes on and achieve some skill and speed. Accept the fact that you will never achieve mastery. Console yourself that few if any writers get even close. But try anyway.
If you follow these suggestions, almost all of what you write will not be excellent. The goal of these (and other) suggestions is for you to develop judgement about what is "sort of good" and what is not. The "sort of good" items can perhaps be revised into something that is very good. And perhaps a fraction of these might be good enough to publish. Focus on these survivors. Even one of these published stories gives you the right to declare yourself an author. And that, at any age, is a wondrous thing.
Well you're young for starters for me when I was young yes I could never finish a book or series I wrote on Fan Fiction the only ones I got through were opened ended by defult or were made to be one short event. I believe this was due to not knowing my ending I just wrote as it came up mostly starting in the middle of the action.
I think it's great you want to do this at nine two books I've found useful would be (1) Writing Demystified by Thomas B Sawyer - while its covering mostly the old TV show Murder she Wrote he really breaks down how a series is written and gives tons of insight into things that also co-align with writing novels, screenplays, ect. (2)Story Trumps Structure by Donald Mass - he is a mix of prepper and pantser meaning he plans a bit but writes with no plan at other points he goes over tips on how to do this so you can finish your book. I've learned before reading his book I was no planner I tried but his mix hybrid style is how I've been doing it my works for years and I'm writing the biggest project ever a book series so....
Just also remember writing is hard you are making it all from nothing or next to it so just get it written take a lot a notes so you can keep track of some important things but just get it down, edit it later, your first (and possibly several thereafter) drafts aren't going to be perfect you can fix it later just get it out and down and you will slowly learn what and who your characters are and dream up far better concepts to express that as you go onward.
If you need somethings to get your writings organized beyond Word a ALOT of folders you can try Y-writer its free and really easy for set up but once you learn your project needs to grow you can do Scrivener it's not a lot of money (I think $60) but it is a massive black hole when you're starting out and your young it might look impossible to use but just use it as a research storage area and filing system with their collections feature I find it best to have copies of my billion notes in Scriv because when I go to the collection I want its just there.
One technique is to aim to write your entire story in a short period of time. Don't worry about getting it perfect; just get to the end before you run out of inspiration. You can always fix problems later. Plan your story enough that you aren't going to get stuck half way through, but not so much that you get bored with it before you've even started. Then set aside some time to write intensively, without distractions.
(This is based on the 'How to Write a Novel in Three Days' technique. More details here: https://interestingliterature.com/2014/11/michael-moorcock-how-to-write-a-novel-in-3-days/ )
You could try giving yourself an extremely ambitious writing goal ("I will write 3,000 words before lunch") and seeing if you can do it; even if you fail, you'll probably achieve more than you would have otherwise.
Also, as a young person, remember that your real goal should be improving your techniques for bigger future projects. It doesn't matter if you write something that wasn't as good as you hoped it would be, or even if you failed to finish, as long as you learned something along the way.