"Will you open the window now, please?"
Translation:Wnewch chi agor y ffenestr nawr, os gwelwch chi'n dda?
Os gwelwch yn dda is very common, the chi being omitted from it as a set phrase.
It is also common for pronouns to be dropped in more formal Welsh, too. You will notice that if you look on some written news items and in the narrative text of many articles and novels. We do not do it routinely on this course, though, which covers a middle of the road Welsh, neither formal nor very informal/slang.