Here I have attached workbook. Please go through it and let me know if it helps you or not.
Go in your dashboard and select any country and you'll be able to see all cities related to that particular country.
There is "Top N" Parameter filter, you can use that filter to find top n value by just putting your value. By Default it is 20.
Can you please attach the file and thanks for looking into this. ( Really appreciate )
Attached workbook here.