幫我改改這句子既文法呀～

In this case, even though the firms know that their goods are expired, they sell them to make profit.

even though / although 逗號之後無須再加連接詞。同中文唔一樣。
e.g. Although she's smart, she is humble.

firms 系復數，動詞無須 +s。

overdue 一般講「エ作」未做，expire 即 die，come to an end 嘅意思，指期限。
e.g. Your project is overdued. I have to deduct 5 points. -- 因為專題習作遲交要扣五分。
e.g. The license is expired. You need to renew it. -- 車牌過期，要換領。

Although the firm knows that the goods are overdue, it still sell them for revenue in this case.

Although the firm knows their goods are overdue, they still sell the goods so as to increase their revenue.

In this case, although the firms know that their goods are overdue, they still sell them so as to make more revenue.