assure(v.)
使确信 
　　　
例句：
John assured me that he was an excellent cook.
约翰要我确信他是个很高明的厨师。

the apple of one's eye
某人的掌上明珠
 
例句：
Mary, as the youngest daughter, is the apple of her parents' eye.
作为家中最小的孩子，玛丽是她父母的掌上明珠。

I con't catch your meaning
我不懂你的意思 
　　
对话：
A: I can't catch your meaning. There are so many terms that I don't know.
B: Sorry. I will explain them to you.
　　　　　　　　 　　　　　　　　 　　　　　　　　 　　　
A：我不懂你的意思，你用了太多的术语。
B：对不起，我会给你解释的。