You can start or join discussions or writing notebook entries both are fine since native speakers can correct you. If you want to chat perhaps the best thing is to write private messages.

I would say:  　　なぜにほんごをべんきょうしますか。　わたしのこたえは「日本に行きたいから」です。

くらんさんはなぜにほんごをべんきょうしますか。 :) But maybe it is better to start a new discussion  for this topic :)

Yes, that was what I wanted to say :)　そのとおりです。 Thank you!　ありがとうございます。