Translation:Please polish my shoes.
わたし (watashi) is always the person speaking. It translates to "I" or "me" in english.
I think what they're referring to is that the pronunciation is a bit strange here...
So the lesson is, No matter how rude is the request, Kudasai-san will polish anything.
Does anyone also notice here the 'watashi no' is pronounced as 'watoshi no'? Is that normal?
It's because the same verb is used for brushing your teeth, as shown later this lesson.
Certainly くつ is not known which plural or not. But if you polish only a left shoe when you are said 'please polish the くつ' from somebody, you are said 'stupid!'.
"Certainly くつ doesn't show if it's singular or plural, but if you only polish the left shoe when someone asks you to polish his/her くつ, s/he will call you stupid."
If it's not explicitly specified in the Japanese sentence, it could translate to either singular or plural.
"You clean my shoes, you get the germs. I stay healthy." This is the only reason why this is in the health section XD