YOU SAID:

He had been acting funny over the last the few days.

INTO JAPANESE

ここ数日間、彼はおかしな行動をとっていた。

BACK INTO ENGLISH

He had been acting strangely for the past few days.

INTO JAPANESE

ここ数日間、彼の様子がおかしい。

BACK INTO ENGLISH

He's been acting weird for the past few days.

INTO JAPANESE

ここ数日間、彼の様子がおかしいです。

BACK INTO ENGLISH

He's been acting weird for the past few days.