Merge columns and add new fields

First step: Unpivot your data

let
    Source = Csv.Document(File.Contents("Acceleration Example.xlsx - Sheet3.csv"),[Delimiter=",", Columns=8, Encoding=1252, QuoteStyle=QuoteStyle.None]),
    #"Promoted Headers" = Table.PromoteHeaders(Source, [PromoteAllScalars=true]),
    #"Changed Type" = Table.TransformColumnTypes(#"Promoted Headers",{{"Opportunity CreatedDate", type date}}),
    #"Unpivoted Other Columns" = Table.UnpivotOtherColumns(#"Changed Type", {"Opportunity ID", "Opportunity CreatedDate"}, "Attribute", "Value"),
    #"Changed Type1" = Table.TransformColumnTypes(#"Unpivoted Other Columns",{{"Value", type number}})
in
    #"Changed Type1"

Next, add the required fields to table visual and set aggregation for the value column to Average: