Combine Data from Multiple Tables to 1 Pivot When Having Duplicate Values

yanlt , the easiest way to combine is by Power Query. Script like this

let
    Source1 = Excel.CurrentWorkbook(){[Name="General"]}[Content],
    Source2 = Excel.CurrentWorkbook(){[Name="Software"]}[Content],
    Source3 = Excel.CurrentWorkbook(){[Name="Mechanics"]}[Content],
    AppendedTables = Table.Combine({Source1, Source2, Source3}),
    ToNumber = Table.TransformColumnTypes(AppendedTables,{
        {"Jan-19", type number},
        {"Feb-19", type number},
        {"Mar-19", type number},
        {"Apr-19", type number},
        {"May-19", type number}})
in
    ToNumber

is generated from User Interface, load that query as connection adding data to data model, and build PivotTable from data model.