I assume your table called “categoryInfo”.
You can create a column called “weekOfYear” to get the week of year from “Week Commencing” in Query Editor. See screenshot below.
Now you can called a measure to calculate the sumAmount by weekOfyear:
sumAmountByWeek = CALCULATE(sum(categoryInfo[Amount]), ALLEXCEPT(categoryInfo, categoryInfo[WeekOfYear]))
Then you can create a measure to calculate max sumAmount:
maxSumWeekAmount = CALCULATE(MAXX(ALL(categoryInfo[WeekOfYear]), categoryInfo[sumAmountByWeek]))