In this task, you have given an input which is user's command or question, based on that you have to return what will be Agent's response/reply for that particular user's command or question

yes exactly
I've deleted your event matching "Dentist appointment" on Monday the 15th.

Do I have any events scheduled on April 1st?
No, I didn't find any events on April 1st.

add something for the 21st at 4 pm, and mark it unknown

I've put that on your calendar. Your status is set to Unknown.