convert Rows to Columns in SQL with same ID, Sql Server

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--TEST DATA
CREATE TABLE #TestTable
    ([TravelID] int, [SitelD] int, [Flagi] int, [FIag2] int)
;
    
INSERT INTO #TestTable
    ([TravelID], [SitelD], [Flagi], [FIag2])
VALUES
    (1001, 1, 1, 0),
    (1001, 1, 0, 1),
	(1001, 1, 3, 4),
	(1002, 1, 1, 0),
    (1002, 2, 0, 1),
	(1002, 2, 3, 4)
;

--STEP 1 rank data
SELECT * into #rank_table from (
    select  *
    ,ROW_NUMBER() OVER (PARTITION BY [TravelID],[SitelD] order by [SitelD]) [rank]
    from (
        select * from #TestTable
    ) T100    
)T;

--STEP 2 Group by row_count
SELECT * into #group_table from (
    select [TravelID],[SitelD] ,count(1) [count]
    from #TestTable T
    group by [TravelID],[SitelD]
)T;

--Use Exec
DECLARE @select_sql AS NVARCHAR(MAX) = ' select  T.[TravelID], T.[SitelD] ',
@join_sql AS NVARCHAR(MAX) = ' from #group_table T ',
@max_count INT = (SELECT max([count]) FROM #group_table),
@temp_string NVARCHAR(5),
@temp_string_addone NVARCHAR(5)
;

DECLARE @index int = 0 ;
WHILE @index < @max_count
BEGIN
    sELECT @temp_string = Convert(nvarchar(10),@index);
   sELECT @temp_string_addone = Convert(nvarchar(10),@index+1);
   select  @select_sql = @select_sql + ' , T'+@temp_string_addone+'.[Flagi] as Flag'+Convert(nvarchar(10),2*@index+1)+' '
	+ ' , T'+@temp_string_addone+'.[FIag2] as Flag'+Convert(nvarchar(10),2*@index+2)+' ';
   select  @join_sql = @join_sql + 'left join #rank_table T'+@temp_string_addone+' on ' + ' T.[TravelID] = T'+@temp_string_addone+'.[TravelID] and '
   + ' T.[SitelD] = T'+@temp_string_addone+'.[SitelD] and '
   + 'T'+@temp_string_addone+'.[rank] = '+@temp_string_addone+' ';
   SET @index = @index + 1;
END;

EXEC (@select_sql
+ @join_sql
+' order by [TravelID],[SitelD] ; ')
;

View schema
Execution time: 0,03 sec, rows selected: 20, rows affected: 6, absolute service time: 0,19 sec