MySQL query conversion to MongoDB

Question

I am new to MongoDB. I have done code to get the highest deaths value country-wise with their reporting date in MySQL. As the initial step, I am trying to get the max value of the deaths column, but it is returning another value that is not the highest. Here is my MySQL code:

SELECT 
d.country_name, s.dt, MAX(s.deaths)
FROM
Demographics d 
inner JOIN statistics s 
where d.country_id=s.country_id
GROUP BY country_name
ORDER BY MAX(s.deaths) DESC;

It is returning:

Germany	2022-01-29	118335
Bangladesh	2022-01-30	34

What will be the equivalent code to MongoDB to get the same result? To get the max value of the deaths column in MongoDB i used:

db.statistics.aggregate([
  {
    $group: {
      _id: "$country_id",
      maxQuantity: {
        $max: "$deaths"
      }
    }
  }
])

Here is my sample input:

Demographics

{"country_id":"BGD","country_name":"Bangladesh","population":"164700000","area":"148460","density":"1265"}, {"country_id":"DEU","country_name":"Germany","population":"83200000","area":"357386","density":"232"}

statistics

{"country_id":"DEU","dt":"2022-01 29", "confirmed_cases":"2016684", "deaths":"118335"},
{"country_id":"DEU","dt":"2022-01-17", "confirmed_cases":"53916", "deaths":"143"}, 
{"country_id":"BGD","dt":"2022-01-30", "confirmed_cases":"12183", "deaths":"34"},
{"country_id":"BGD","dt":"2022-01-29", "confirmed_cases":"10378", "deaths":"21"},