Transpose + Unpivot colums

See the working here - Open a blank query - Home - Advanced Editor - Remove everything from there and paste the below code to test (later on when you use the query on your dataset, you will have to change the source appropriately. If you have columns other than these, then delete Changed type step and do a Changed type for complete table from UI again)

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("VYy7DcAgEMV2uZqG3wAJ+a+A2H+N+PQKRGHJbty7tWjBNog2ApnQHZIyow2ysqAHFGVFT6hKX13r6l5Xz0xfvfPsq0+r8QM=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Column1 = _t, Column2 = _t, Custom = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Column1", type text}, {"Column2", type text}, {"Custom", Int64.Type}}),
    #"Removed Columns" = Table.RemoveColumns(#"Changed Type",{"Custom"}),
    #"Added Index" = Table.AddIndexColumn(#"Removed Columns", "Index", 1, 1, Int64.Type),
    #"Divided Column" = Table.TransformColumns(#"Added Index", {{"Index", each Number.RoundUp(_ / 5,0), type number}}),
    #"Pivoted Column" = Table.Pivot(#"Divided Column", List.Distinct(#"Divided Column"[Column1]), "Column1", "Column2"),
    #"Removed Columns1" = Table.RemoveColumns(#"Pivoted Column",{"Index"})
in
    #"Removed Columns1"