Today

I am staying in Australia on a working holiday.

You can also just say "I'm in Australia on a working holiday"

I arrived here three days ago.

Sometimes sentence patterns in English are the reverse of the sentence patterns in Japanese.

Today I was going to study English for school.

In Japanese you usually omit "私" from a sentence, but in English we often say "I" in conversation.

But my English is so bad...

"Too bad"というのは、”残念”という意味なんです。e.g. Smith: I wanted to buy the new iPad, but they were all sold out. Tom: Oh, that's too bad. Have you tried looking in other shops? 日本語：スミス：新しいアイパッド、買いたかったんだけど売れ切れだった。トム：それは残念だね。他の店で売っているかどうか見てみたら？

If I could speak English,I would talk more.

Both clauses need the conditional.

どういう意味ですか。

Do you mean "Finally I hope I can talk to many people!!"?

I will study much more(^▽^)o