--5ta
SELECT [Description], FORMAT(OpenDate, 'dd-MM-yyyy') FROM Reports
WHERE EmployeeId IS NULL
ORDER BY OpenDate, [Description]
--6ta
SELECT r.[Description], c.[Name] FROM Reports r
JOIN Categories c ON c.Id = r.CategoryId
ORDER BY r.[Description], c.[Name]

-7ma
SELECT TOP(5) c.[Name], COUNT(*) AS [ReportsNumber] FROM Reports r
JOIN Categories c ON c.Id = r.CategoryId
GROUP BY c.[Name]
ORDER BY [ReportsNumber] DESC, c.[Name]