YOU SAID:

My chair could not stand straight until I wrote my letter.

INTO JAPANESE

私が私の手紙を書くまで私の椅子はまっすぐに立つことができなかった。

BACK INTO ENGLISH

My chair could not stand straight until I had written my letter.

INTO JAPANESE

私が自分の手紙を書くまで私の椅子は直立できませんでした。

BACK INTO ENGLISH

My chair could not stand upright until I wrote my letter.

INTO JAPANESE

私が私の手紙を書くまで私の椅子は直立できなかった。

BACK INTO ENGLISH

My chair could not stand upright until I wrote my letter.