David cooked so well

[Bassim]

Have I made any mistakes?

David cooked so well that people used to say he could make his fortune in the restaurant business. He replied that that might be true, but running a restaurant took a lot of time, so what he would do with money but no spare time. He knew some people who had restaurants, and they hardly had time for themselves and their families.

 

[Tarheel]

Have I made any mistakes?

David cooked so well that people used to say he could make his fortune in the restaurant business. He replied that that might be true, but running a restaurant takes a lot of time, so what would he do with money but no spare time? He knew some people who had restaurants, and they hardly had time for themselves and their families.

It's OK.

 

[teechar]

David cooked so well

I would much prefer something like:
David was such a skillful cook
or
David's cooking skills were so good

he could make [STRIKE]his[/STRIKE] a fortune in the restaurant business. He [STRIKE]replied[/STRIKE] accepted that, [STRIKE]that might be true,[/STRIKE] but to him, running a restaurant took a lot of time, so what [STRIKE]he would do with[/STRIKE] good would money be if that meant having [STRIKE]but[/STRIKE] no spare time. He knew [STRIKE]some people who had[/STRIKE] (several) restaurateurs [STRIKE]s, and they[/STRIKE] who hardly had time for themselves and their families.

Try that.

 

[Tarheel]

Running a restaurant took a lot of time.

That's past tense. I would only use that if it were not true anymore. Or, if applied to a specific person, that person is not in the restaurant business anymore.