business is declining

Hi,

If I want to say that a business is getting worse. Is decline a good word there. Can I say this(I add a context):

'John is not doing well at work. His business activity is declining. I mean his sale is declining and ... ' --> is it in order?

Is it OK to say:
The standards of living are declining.(?)

thanks!

Yes you can. It would be more normal to express it in the plural, as in "His business activities are declining" [and you would always talk about "sales" rather than "sale" . You could also say it as "... is/are in decline". The same goes for "Standards of living".