Select Rows based on Timestamp in one table and Start End Fields on a Second Table

I spent around 2 hours with this query. I tried different versions of code because I wanted to speed it up, but txt source is too slow and you need to do a lot of comparism. I'm not able to make it faster. Maybe someone else can help.

Change address to your folder in Source step.

let
Source = Folder.Files("c:\Downloads\PowerQueryForum\VHalpenny\"),
    FilteredSessionsTable = Table.SelectRows(Source, each ([Name] = "SessionsTable.xlsx")),
    Content = FilteredSessionsTable{0}[Content],
    ImportedExcelWorkbook = Excel.Workbook(Content, true),
    Sheet1 = ImportedExcelWorkbook{[Item="Sheet1",Kind="Sheet"]}[Data],
    FilteredRows1 = Table.SelectRows(Sheet1, each ([T200] <> null)),
    RemoveMiliseconds = Table.TransformColumns(FilteredRows1, List.Transform({"T200", "T300"}, (x)=> { x, each DateTime.From(DateTime.ToText(_, [Format="yyyy-MM-dd hh:mm:ss"])) })),
    Ad_DateTimeList = Table.AddColumn(RemoveMiliseconds, "DateTimeList", each List.DateTimes([T200], Duration.TotalSeconds([T300] - [T200])+1, #duration(0,0,0,1)), type list),
    Ad_MergeKey1 = Table.AddColumn(Ad_DateTimeList, "MergeKey", each 
        if Time.Minute([T200]) = Time.Minute([T300])
        then { Number.From(DateTime.ToText([T200], "yyyyMMddhhmm")) }
        else { Number.From(DateTime.ToText([T200], "yyyyMMddhhmm")), Number.From(DateTime.ToText([T300], "yyyyMMddhhmm")) },
    type list),
    // Niektore riadky su zduplikovane kvoli MERGE neskor. Jedna sa o riadky kedy minuta z [T200] nie je rovna minute z [T300]
    ExpandedMergeKey1 = Table.ExpandListColumn(Ad_MergeKey1, "MergeKey"),
    TableSessions = Table.Buffer(Table.SelectColumns(ExpandedMergeKey1,{"Operator", "MergeKey", "DateTimeList"})),
    StepBack = Source,
    FiteredOperatorTextFiles = Table.SelectRows(StepBack, each Text.StartsWith([Name], "Operator", Comparer.OrdinalIgnoreCase) and [Extension] = ".txt" ),
    RemovedOtherColumns1 = Table.SelectColumns(FiteredOperatorTextFiles,{"Content", "Name"}),
    Ad_Data = Table.AddColumn(RemovedOtherColumns1, "Data", each 
        [ a = Table.TransformColumnNames(Table.PromoteHeaders(Csv.Document([Content],[Delimiter=";", Columns=3, Encoding=1250, QuoteStyle=QuoteStyle.None])), Text.Trim), //csv to table + promote headers + trim column names
          b = Table.AddColumn(a, "Operator", (x)=> Text.BeforeDelimiter([Name], "_"), type text), //Add Operator column
          c = Table.AddColumn(b, "System", (x)=> Text.Proper(Text.BetweenDelimiters(Text.Lower([Name]), "_", ".txt")), type text) //Add System column
          //d = Table.FirstN(c, RepeatValue) //for query creating purpose (to load less data)
        ][c], type table),
    CombinedData = Table.Combine(Ad_Data[Data]),
    ChangedType = Table.TransformColumnTypes(CombinedData,{{"Time", type datetime}, {"MR-DC DRB PDCP DL Throughput Total (kbps)", type number}, {"MR-DC DRB PDCP UL Throughput Total (kbps)", type number}}, "en-US"),
    FilteredRows2 = Table.SelectRows(ChangedType, each [Time] <> null),
    RemoveMiliseconds2 = Table.TransformColumns(FilteredRows2, {{"Time", each DateTime.From(DateTime.ToText(_, [Format="yyyy-MM-dd hh:mm:ss"]))}}),
    Ad_MergeKey2 = Table.AddColumn(RemoveMiliseconds2, "MergeKey", each Number.From(DateTime.ToText([Time], "yyyyMMddhhmm")), Int64.Type),
    GroupedRows = Table.Group(Ad_MergeKey2, {"Operator", "MergeKey"}, {{"All", each _, type table [Time=nullable datetime, #"MR-DC DRB PDCP DL Throughput Total (kbps)"=nullable number, #"MR-DC DRB PDCP UL Throughput Total (kbps)"=nullable number, Operator=text, System=text, Date=date, Hour=number]}}),
    MergedQueries = Table.NestedJoin(GroupedRows, {"Operator", "MergeKey"}, TableSessions, {"Operator", "MergeKey"}, "TableSessions", JoinKind.LeftOuter),
    FilteredRows3 = Table.SelectRows(MergedQueries, each Table.RowCount([TableSessions]) <> 0),
    Ad_TableSessionDateTimes = Table.AddColumn(FilteredRows3, "TableSession_DateTimes", each List.Combine([TableSessions][DateTimeList]), type list),
    RemovedOtherColumns2 = Table.SelectColumns(Ad_TableSessionDateTimes,{"All", "TableSession_DateTimes"}),
    ExpandedAll = Table.ExpandTableColumn(RemovedOtherColumns2, "All", {"Time", "MR-DC DRB PDCP DL Throughput Total (kbps)", "MR-DC DRB PDCP UL Throughput Total (kbps)", "Operator", "System"}, {"Time", "MR-DC DRB PDCP DL Throughput Total (kbps)", "MR-DC DRB PDCP UL Throughput Total (kbps)", "Operator", "System"}),
    Ad_KeepRow = Table.AddColumn(ExpandedAll, "Keep Row", each List.Contains(List.Buffer([TableSession_DateTimes]), [Time]), type logical),
    FilteredRows4 = Table.SelectRows(Ad_KeepRow, each [Keep Row] = true)
in
    FilteredRows4