CSV Web connection doesn't update my report properly

Try replacing your Origin line with:

Origin = Csv.Document(Web.Contents("https://raw.githubusercontent.com/CSSEGISandData/COVID-19/master/csse_covid_19_data/csse_covid_19_time_series/time_series_19-covid-Confirmed.csv")),

This gets rid of the definition for how many columns there are. That being said, you will have to be careful with the rest of your query. A dynamic set of columns is not the most pleasant thing to deal with. It can play havoc with the rest of your query. I would promote the first row and then immediately use unpivot other columns to unpivot the day columns. Also get rid of any automatic Change Type step. Use something like the following for the first part of your query:

let
    Source = Csv.Document(Web.Contents("https://raw.githubusercontent.com/CSSEGISandData/COVID-19/master/csse_covid_19_data/csse_covid_19_time_series/time_series_19-covid-Confirmed.csv")),
    #"Promoted Headers" = Table.PromoteHeaders(Source, [PromoteAllScalars=true]),
    #"Unpivoted Other Columns" = Table.UnpivotOtherColumns(#"Promoted Headers", {"Province/State", "Country/Region", "Lat", "Long"}, "Attribute", "Value"),
    #"Renamed Columns" = Table.RenameColumns(#"Unpivoted Other Columns",{{"Attribute", "Day"}}),
    #"Changed Type" = Table.TransformColumnTypes(#"Renamed Columns",{{"Value", Int64.Type}, {"Day", type date}})
in
    #"Changed Type"