Learning Japanese easily?

I am an above-average intelligence for a 14-year-old and I was hoping to learn Japanese. Japanese is a quite challenging language. I would like to learn it to be able to understand the animes I watch without subs (I think it would be fun) and it would be useful to learn at this age instead of later on, in case I need to use it later in life. I have tons of time on my hands and I thought, "Why not do something useful with it?' I tried watching non-subbed anime I was unfamiliar with but that did nothing, as I don't know anything about the language. I'm American, and I don't know anyone who fluently speaks the language. My friend also wants to learn the language so I was thinking we could collaborate and speak to each other in Japanese when we can, try to write it, and so on. Are there any alternative ways to learn that we could use to up our knowledge? For example, how does the grammar work? The letters? Might there be some workbooks at a Barnes and Nobles? I would look for something not too terrifyingly hard, as I do have ADHD and will not be able to focus for long amounts of time. Are there strategies to use so I won't have to focus a bunch, or just soak it in? If not, I'll be open to it anyways! Thanks! :)
Added (1). I realize my grammar was incorrect in the first sentence. *have

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