Changing columns types except selected ones

Hello All, 

I have the following table: 

I am trying to create a function that would change the column types of all columns expceted the columns Brand and Category. 

(The other column's names will always change. The column "Brand" and "Category" will always be the 2 first columns and their names will never change)

I have tried the following function but doesn't work: 
        = Table.TransformColumnTypes(#"End stage 3",
List.Transform(
List.RemoveFirstN(
Table.ColumnNames(Source),
2
),
each {_, Int64.Type}
))

I get an error message : "Expression.Error: The column 'Item' of the table wasn't found.
Details:
Item"

but nowhere in my table or transformations I have a column names Item. 

Anyone has an idea how I could achieve this?