1.I'm trying to improve my English through chatting online in English.

　　我正通过网上聊天来提高我的英语。

　　2.You enjoy staying with girls and study English at the same time. That's called "Kill two birds with one stone."

　　泡妞和学习，一箭双雕。

　　3.I have forgotten what I have learned, but I have confidence to learn it well.

　　学过的东西(英语)我全忘了，但我有信心很快学好。