Speeding up power query

I previously got help creating a query for calculating a weighted average for missing values in my table in this post.

My table has 550 000 rows and the query has been running since tuesday on my I7-7700K and is not finished yet.

With only the top 1000 rows the query finishes in about 6-7 minutes.

Is there a way to speed up this query? As i get it, for every row the entire table is filtered and sorted.

This is from the example data created in my previous post (just for reference)

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjRQ0lHyqAAShgYgpquhUqwOTLgSSBhBhI3AwpYIxQi1cEEjdJUg/cZgQWOwoAVcuylCO1zQyBSh3QKu3RSqPRYA", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type text) meta [Serialized.Text = true]) in type table [Analysis = _t, Quality = _t, Value = _t, Element = _t]),
    AnalysisAsInt = Table.TransformColumnTypes(Source,{{"Analysis", Int64.Type}}),

    LastTwoAnalysis = Table.AddColumn(AnalysisAsInt, "LastTwoAnalysisTable", 
        (parentRow as record) =>
            Table.FirstN(
                Table.Sort( 
                    Table.SelectRows(AnalysisAsInt, 
                        (childRow as record) => 
                            childRow[Quality] = parentRow[Quality] 
                            and 
                            childRow[Element] = parentRow[Element]
                            and
                            childRow[Analysis] < parentRow[Analysis]
                    ),
                {{"Analysis", Order.Descending}}
            ),
            2
        )
    )
in
    LastTwoAnalysis