I think you did a great job if this is the first one :)

Keep practicing and you'll get better and better!!

こんにちわは！

わたしわはひらがなありますならわかります。

にほんごのべんきょうわはたも氏おもしろいです！

はほんとうに！

わたしわはあめりかのじんせいじんです。

いぢょいじょうです！^_^

<em>[Quick Tips]</em>

(1)　"ha" and "wa"

It's true that "は" right after the subject is pronouced like "wa".

But you should write ”は”, not "わ".

(2) "interesting"

The translation of "interesting" is "おもしろい [Omoshiroi]" or "きょうみぶかい [Kyoumibukai]".

And translation of "fun" is "たのしい".

こんにちわ！ 

わたしわ ひらがな あります。にほんごわ たも氏です！ はんとに！わたしわ あめりかの じんせい です。いぢょです！^_^

Hello (Good afternoon)!

I only know hiragana. Japanese is really interesting! Really! I am from America as well. That is all!

*it is really short, but it's a start!*