Has anyone here learned Japanese, and if so, do you have any advice?
Sukoshi demo mada joozu jaa arimasen
Yes. Do two things:
1) Take a class at your local community college. They'll be at night, so they won't interfere with school. They'll be cheap, probably under $200. And they'll definitely give you school credit...since you'l be taking a college course at a college. Yes, you can take college classes while in high school.
2) Get the
Pimsleur CD set. It is
vastly superior to anything else out on the market because it drills you using complete sentences at conversational speed from day one. It won't give you a huge vocabulary...that's what the class is for. But it will set you on the path to good pronunciation and the ability to listen to, and make sentences without stumbling over every word. If possible, I recommend getting physical CDs rather than torrenting them. Very clear audio is important, and ripped audio tracks tend to be less clear than CD. You don't want to be guessing at vowel sounds because you're listening to low resolution recording. Try your local public library. Mine has an entire section for language learning CDs. Yours might too.
Incidentally, if you want to try before you buy/acquire, here's
lesson 1 on youtube. When you do it...don't just listen.
Interact with it. The silent parts are for you to speak aloud. Do that.
I'm nearly done learning katakana
That's not very useful. Katakana is only used for words that aren't native to Japanese and in some cases to emphasize words in marketing copy, sort of like italics. Learn hiragana. It's used for words that are actually Japanese.
I do not know any kanji at this point
Don't worry about that yet. Kanji will be learned as you go while taking the classes. I advise that you
don't try to learn kanji on your own. There are some major conceptual things going on that need to be understood. You can't just memorize characters and expect them to mean anything. Kanji doesn't work that way. Unlike English letters, which represent sounds, kanji characters represent
ideas. For kanji to make
any sense, you'll need to already understand the language and words that the characters relate to.
If you have more specific questions, ask them.