前置詞 into/in/out of
Inは、中にいる/ある状態で動きはなく、Intoは、中に向かって動いているイメージです。
Intoした結果inになる感じ。inも動きがあると思える時に使うことはあります。
In, intoの反対がout of 。何かの外にいる/ある状態で動きがない場合、中から外にでる動きを表す場合の両方で使えます。
赤ずきんちゃんをイメージした例文を作ってみました：
Little Red Riding Hood went into the woods. While she was in the woods, she met a cunning wolf who wanted to eat her. But she was able to get out of trouble by running away as fast as she could.
次の例では、水の中に入っていく動きを表すintoと水の中にいたという動きがないin、水が冷たいので自ら出たという動きがあるout ofと午後ずっと水の外にいたという動きがないout ofを確認してください：
I went to the sea for a swim yesterday. I went into the water but it was quite cold, so I got out of the water and stayed out of it all afternoon. I must have been in the water for less than a minute.
恋に落ちる時や、お付き合いしている状態もinとout ofで表せます：
I fell in love with her when I first met her. It was a love at first sight. We were in a relationship for a while, but when I realised she was only after my money, I quickly got out of it.
状態もinto (in) とout ofが使えます：
When he invested too much money, he got himself into a sticky situation. Luckily, his parents gave him a loan so he was able to get out of it.
In は副詞の意味もありますが、Outは副詞の意味の場合が多く、outだけで前置詞の意味として使われることは、イギリス英語ではほとんどありません。
副詞の意味のinとoutの例：
Matt: Hello. This is Matt. Is Sandy in?
Todd: She’s out at the moment. Could I take a message?
Sarah is a good swimmer. She just dived in and swam out to the other side of the lake.
Into, in, out ofのイメージを定着させ、口からさっと出るようにするためにも、部屋に行ったり、どこかの建物に入る時、'I'm going into the kitchen. I'm in the kitchen. I'm going out of the kitchen. I'm out of the kitchen.' などと言って練習してみてください。