I can't waste time on such frivolities.

我不能把时间浪费在这种无聊的活动上。

I don't want to waste time on trivialities.

我不想把时间浪费在一些琐碎小事上。

You all know why I am here. So I won't waste time on preliminaries.

你们都知道我为什么在这里。所以我就不浪费时间讲客套话了。

You all know why I am here, so I won't waste time on preliminaries.

你们都知道我为什么来这儿，因此我就不浪费时间作介绍了。

There could be many reasons and he was not going to waste time speculating on them.

原因可能很多，而他不打算浪费时间猜测这些原因。