首先，我想问你几个关于你童年时期的问题。

___First ___of ___all, I'd like to ask you a few questions about your childhood.

首先，谢谢你的来信。

___First ___of ___all, thanks for your letter.

首先，让我自我介绍一下。

___First ___of ___all, let me introduce myself.