Power Query Data Transformation

alir22456 Try this:

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45Wci4tLsnPTS1SMFTSUQooyk8pTS4BsmN1cEgZ4ZYyRpUywm2gEW4DjXHrMiZOlzFuKROl2FgA", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Customer = _t, Product = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Customer", type text}, {"Product", type text}}),
    #"Grouped Rows" = Table.Group(#"Changed Type", {"Customer"}, {{"Products", each _, type table [Customer=nullable text, Product=nullable text]}}),
    #"Added Custom" = Table.AddColumn(#"Grouped Rows", "Custom", each Table.Transpose(Table.SelectColumns([Products], "Product"))),
    #"Expanded Custom" = Table.ExpandTableColumn(#"Added Custom", "Custom", {"Column1", "Column2", "Column3", "Column4"}, {"Column1", "Column2", "Column3", "Column4"}),
    #"Removed Columns" = Table.RemoveColumns(#"Expanded Custom",{"Products"})
in
    #"Removed Columns"