YOU SAID:

My brother is writing stupidities into game chat.

INTO JAPANESE

私の弟はゲーム チャットに愚かさを書いています。

BACK INTO ENGLISH

My brother wrote the stupidity in game chat.

INTO JAPANESE

私の兄は、ゲームのチャットで愚かさを書いた。

BACK INTO ENGLISH

My brother wrote the stupidity in game chat.