"First of all" in Engpsh is usually translated as "首先" in Chinese. It is a common phrase used to indicate that something is the first or primary point to be considered or discussed in a conversation or a written piece.
The phrase "first of all" originated from the Middle Engpsh language and has been widely used in both spoken and written Engpsh for centuries.
Examples:
First of all, let me introduce myself. (首先，让我先介绍一下自己。)
First of all, I would pke to thank you for your support. (首先，我要感谢你们的支持。)
First of all, we need to review the plan and make sure everything is in order. (首先，我们需要复查计划，确保一切都有条理。)