Get the first value of multiple days

Hi Lazurens 

See if this works for you, just copy the full script into a new blank query.

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjTWNTDRNTJW0lEyNzc3NDUBMiwNgIShgYFSrA5QgQkOBUbmEHlTHPJA7bEA", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Date = _t, NumFO = _t, TimeObs = _t, #"TimeReal " = _t]),
    ChType = Table.TransformColumnTypes(Source,{{"Date", type date}, {"NumFO", Int64.Type}, {"TimeObs", Int64.Type}, {"TimeReal ", Int64.Type}}),
    GroupRows = Table.Group(ChType, {"NumFO"}, {{"t", each 
        [
            a = Table.Sort( _,{{"Date", Order.Ascending}}),
            b = Table.ReplaceValue(a,each [TimeObs],each if a[Date]{0} = [Date] then [TimeObs] else 0,Replacer.ReplaceValue,{"TimeObs"})
        ][b] }}),
    Expand_t = Table.ExpandTableColumn(GroupRows, "t", {"Date", "TimeObs", "TimeReal "}, {"Date", "TimeObs", "TimeReal "})
in
    Expand_t

Grouped the data on NumFO, included a sort just in case and updated the value in the TimeObs column.

with this result.

I hope this is helpful