YOU SAID:
I'm so happy he's been more active lately.
INTO JAPANESE
彼が最近もっと活発になっていることをとてもうれしく思います。
BACK INTO ENGLISH
I am very pleased that he has become more active lately.
INTO JAPANESE
彼が最近もっと活発になったことをとてもうれしく思います。
BACK INTO ENGLISH
I am very pleased that he has become more active lately.
That didn't even make that much sense in English.