SQL Server 2019

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DROP TABLE IF EXISTS #TempDestinationTable 
DROP TABLE IF EXISTS ##TempResultTable

DECLARE @cols AS NVARCHAR(MAX) = ''      
,@query  AS NVARCHAR(MAX);

DECLARE @TabRecord NVARCHAR(100)='{"firstName":"Bill","lastName":"Gates","skills":["C#","SQL"]}'

SELECT [key] AS ColumnName      
,value       
INTO #TempDestinationTable      
FROM OPENJSON(@TabRecord);

SET @cols = STUFF((SELECT distinct ',' + QUOTENAME(c.[ColumnName])       
	FROM #TempDestinationTable c      
	FOR XML PATH(''), TYPE      
	).value('.', 'NVARCHAR(MAX)')       
,1,1,'')

DECLARE @TableProperty NVARCHAR(MAX)=  REPLACE(@cols, ',', ' NVARCHAR(MAX),')      
SET @TableProperty  = @TableProperty+' NVARCHAR(MAX)'      
DECLARE @TableQuery NVARCHAR(MAX)= 'CREATE TABLE ##TempResultTable ('+@TableProperty+')'      
EXEC(@TableQuery)

set @query = 'SELECT ' + @cols + ' from       
    (      
     select value, ColumnName      
     from #TempDestinationTable      
      ) x      
    pivot       
    (      
     max(value)      
     for ColumnName in (' + @cols + N')              
    ) p '      
      
 INSERT INTO ##TempResultTable      
 execute(@query)  
 
SELECT * FROM ##TempResultTable

DROP TABLE IF EXISTS #TempDestinationTable
DROP TABLE IF EXISTS ##TempResultTable

firstName	lastName	skills
Bill	Gates	["C#","SQL"]