SELECT
    DATEFROMPARTS(YEAR(CreationDate), MONTH(CreationDate), 1), 
    SUM(IsQuestion) AS Questions,
    SUM(IsAnswer) AS Answers
FROM (
SELECT CreationDate, 
   CASE PostTypeId WHEN 1 THEN 1 ELSE 0 END AS IsQuestion,
   CASE PostTypeId WHEN 2 THEN 1 ELSE 0 END AS IsAnswer
--   CAST(PostTypeId = 2 AS Int) AS IsAnswer
--  IF(PostTypeId = 1,1,0) AS IsQuestion,
--  IF(PostTypeId = 2,1,0) AS IsAnswer
FROM PostsWithDeleted
WHERE
          CreationDate >= '2025-01-01'
      AND CreationDate < '2026-05-07'
) AS Posts_
GROUP BY DATEFROMPARTS(YEAR(CreationDate), MONTH(CreationDate), 1)
ORDER BY DATEFROMPARTS(YEAR(CreationDate), MONTH(CreationDate), 1) DESC;

https://data.stackexchange.com/stackoverflow/query/1931019/question-asked-by-month#graph