もし私の英語におかしな表現、またはもっとよい表現があれば教えてください
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基本的に、直前の行為への感謝は「ありがとうございます」、相手が過去の行為への感謝は「〜ました」になります。
使い分け方法としては、「ありがとうございました」は相手との会話が終わる直前に使うと考えるといいかもしれません。たとえばコンビニのレジで店員が出て行くとき、電話を切るときなどです。
ただ、日本人はそこまで厳密に区別して使いません。入れ替えても意味が通じるケースが多いですよ。
Please let me know when you feel my English expression is unnatural or there is much better expression.
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Basically, to express thanks to a person for his/her action to have done just before, just say “Arigatou Gozaimasu”. To express thanks to a person for his/her action done before, just say “something (an act) arigatou gozaimashita”.
It may be better to think using expression “arigatou gozaimasu” right before ending the communication with a person speaking to. For example, say “arigatou gozaimasu” just before a customer leaves a convenience store and right before hanging up a telephone.
However, Japanese do not use that expression with such strict distinction. There are many occasions in which swapping those expression does not matter to understand what a speaker wants to express.
