transforming excel sheet in power query editor

I'm reasonably sure you don't really want to do this (in power query at least).

If you did do it and if you want do anything with those new columns, you'll have to write a measure for each column => 1311 measures.

Also, what happened to row with Notification 300642957?

I am assuming that you must have multiple rows with the same notification but different Stat and Date, and that your example is not realistic.

Perhaps a more realistic data source would look like:

That being the case, the below might be what you want:

let
    Source = Excel.CurrentWorkbook(){[Name="Table2"]}[Content],
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Notification", Int64.Type}, {"Stat.", type text}, {"Date", type date}}),
    
//will be used below in Pivot
    Stats = List.Sort(List.Distinct(#"Changed Type"[#"Stat."])),

    fieldTypes = List.Repeat({type nullable date}, List.Count(Stats)),
    rowColumnTypes = List.Transform(fieldTypes, (t) => [Type = t, Optional = false]),
    rowType = Type.ForRecord(Record.FromList(rowColumnTypes, Stats),false),

    #"Grouped Rows" = Table.Group(#"Changed Type", {"Notification"}, {
        {"Pivot", each Table.Pivot(_, Stats,"Stat.","Date"), type table rowType}}),
    #"Expanded Pivot" = Table.ExpandTableColumn(#"Grouped Rows", "Pivot", Stats)
in
    #"Expanded Pivot"

producing:

UPDATE: 
I tried the M-code given in the earlier comment. It got me the correct format, however it got rid of most of my data. Unfortunatly, I now have 6 columns and 268 rows, despite me changing it to "column profiling based on entire data set".
I havent lost hope yet! I still have 8 hours left in the work day! 

Any more ideas to help this new intern out? Thank you!