Count occurrence of specific string

My bad, here's the revised version.

let
    Source = Excel.CurrentWorkbook(){[Name="Table1"]}[Content],
    getFields = Table.AddColumn(Source, "Custom", each 
        [ 
            s = List.Select( Text.SplitAny( [Actie], "#(cr)#(lf)"), each Text.EndsWith(Text.Trim(_), ":")),
            l = Table.FromRecords( List.Transform(s, (x)=>
                let t = Text.Split(x, " ") in 
                [
                    Date = t{0}?, 
                    Agent = Text.Combine( List.Skip(t, 2), " ")
                ]
            )),
            n = Table.RemoveRowsWithErrors(Table.TransformColumnTypes( l, {{"Date", type date}}), {"Date"})
        ][n])[Custom],
    Combine = Table.Combine(getFields),
    NoBlanks = Table.SelectRows(Combine, each [Date] <> null and [Date] <> ""),
    GroupRows = Table.Group(NoBlanks, {"Date", "Agent"}, 
        {
            {"Count", each Table.RowCount( _ ), Int64.Type}
        }
    )
in
    GroupRows