Whenever you do a native check or are checking a translation, there is a rule that you only change what needs changing. I didn't actually know this until I had someone coach me through a job, but it's a rule that makes a lot of sense, and saves a lot of trouble. It's not only useful for translation, but also other people's writing. Put simply, the aim is to do as little as possible. That way you keep the original author's words, and only improve on the places that need it, not the places that may need it. Don't change things if you don't have to.