The best way to handle durations is to convert it to a decimal (in days), load your table, write your DAX measures to do aggregation, and then format it at the end. You can do the first step with a custom column in the query editor with this expression.
= Number.FromText(Text.BeforeDelimiter([Duration], ":"))/24/60 + Number.FromText(Text.AfterDelimiter([Duration], ":"))/24/60/60
Then use the approach in this article to FORMAT as a time value however you like.
Calculate and Format Durations in DAX – Hoosier BI