Let's start with item number one.
让我们先开始第一个事项。
I'd like to start with item number one.
我想先开始第一个事项。.
Why don't we begin with item number one?
我们为什么木先开始第一个事项呢*r
Could we take item one first?
我们可以先开始第一个事项吗？

The issue is about the expansion of our business.

这是关于我们业务扩展的问题。
The issue here is that expansion would be disastrous.
现在的问题是，扩展业务可能会带来严重的后果。
The issue here is that any expansion would be possible.
现在的问题是，任何扩展都有可能。