Improve performance to refresh data power query - multiples files

Hello twister8889 

then your problem is not Power Query and your code but your infrastructure, and on this regard I cannot help you. You have to talk to your administrators. 

Something about your code... I cannot see that you are creating your date-columns out of the filename but you create a static date column by using this syntax

#"Inserted Literal" = Table.AddColumn(#"Extracted Text Between Delimiters", "Date", each "01/01/2020", type text),

 You add a new column named "date" and adding a text-value. Then you are using the date-column for creating all your other columns like year etc. As edhans  is also mentioning is that in a datamodel is better to avoid redundant data and this means that is better to create a date-dimension with all your data (like year) and then connect to your fact table through your date-column.

About your performance you can try this code... maybe it's faster

let
Source = Folder.Files("C:\Users\User01\Desktop\Folder1\New Folder Performance"),
#"Filtered Hidden Files1" = Table.SelectRows(Source, each [Attributes]?[Hidden]? <> true),
#"Invoke Custom Function1" = Table.AddColumn(#"Filtered Hidden Files1", "Transform File from New Folder Performance", each #"Transform File from New Folder Performance"([Content])),
#"Removed Other Columns" = Table.SelectColumns(#"Invoke Custom Function1",{"Name", "Transform File from New Folder Performance"}),
#"Expanded Transform File from New Folder Performance" = Table.Buffer(Table.ExpandTableColumn(#"Removed Other Columns", "Transform File from New Folder Performance", {"Clients", "Stock", "Cash"}, {"Clients", "Stock", "Cash"})),
#"Extracted Text Between Delimiters" = Table.TransformColumns(#"Expanded Transform File from New Folder Performance", {{"Name", each Text.BetweenDelimiters(_, "_", "_"), type text}}),
#"Inserted Literal" = Table.AddColumn(#"Extracted Text Between Delimiters", "Date", each "01/01/2020", type text),
#"Changed Type" = Table.TransformColumnTypes(#"Inserted Literal",{{"Date", type date}}),
#"Inserted Month Name" = Table.AddColumn(#"Changed Type", "Month Name", each Date.MonthName([Date]), type text),
#"Inserted Year" = Table.AddColumn(#"Inserted Month Name", "Year", each Date.Year([Date]), Int64.Type),
#"Inserted Merged Column" = Table.AddColumn(#"Inserted Year", "Month", each Text.Combine({[Month Name], Text.From([Year], "pt-PT")}, "-"), type text),
#"Inserted Day" = Table.AddColumn(#"Inserted Merged Column", "Day", each Date.Day([Date]), Int64.Type)
in
#"Inserted Day"

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Have fun

Jimmy