Is this sentence ok? Can you help me fix it?

[Sythr]

Context: I’m creating a website and in the “Contact” section I’d just like to say that it’s ok to message me in Japanese too (even though I’m not so good at it yet). Would this sentence serve that purpose?

日本語で書いてもいいです！私はまだ上手ではないですが、大いに頑張ります。よろしくお願いします。

I have so many questions. I mean I think this is comprehensible enough, but I don’t want it to sound too broken if possible.

1. Is 書く correct here? Would メール/メッセージをする make more sense? In Portuguese I can say “you can write me in Japanese too” with the implied meaning that “writing me” is “sending me a message” and I think it’s fine in English too but I don’t know if it works in Japanese.
2. Should I drop 私は or keep it? Sounds ok without it but I’d rather avoid any misunderstanding.
3. Is ではない too formal? Should I go with じゃない instead?
4. Does 大いに頑張ります sound weird? I didn’t want to use just 頑張ります because I want to emphasize that I really try, but I don’t know if 大いに is good for that or not. (Maybe it’s just too much?)
5. I have a feeling I should end this with よろしくお願いします BUT I’m not really sure why? So please correct me if I’m wrong.

I’m in no hurry whatsoever so if any kind soul can help me here please know that there’s no rush. And thanks in advance!

[Saida]

Hey, I like the overall structure of your message, but I would tweak it a little bit:

1. I agree that 日本語でメッセージをしてもいい sounds better.

2. I would change わたしは to 日本語が, maybe? Also steer clear of 上手？ 日本語がまだまだですが…

3. I would probably go for じゃない、or avoid it completely, like I did up there.

4. おおいに is not used very often. Also 頑張る already implies trying hard. But I would put it in present tense, like so: 頑張っています。You could add a 毎日 or すごく.

5. よろしくお願いします seems fitting to me here. You’re asking your reader to engage with you, so asking for good relations does not seem weird to me.

[Sythr]

Thank you so much, this was really helpful. (And so fast too!) Appreciate it.