Group by Name and sum column radnisati and prekovremeni sati

Question

Code from sql working fine

I need sum column  radni sati and column prekovremeni sati

SUM (cast(radni_sati as float)) as Ukpuno_radni_sati

group by radnik...something like this...

SELECT a.IdPrijava, a.redni_broj , a.radnik, isnull(convert(varchar(20), a.vrijemeodjave, 113), '') as vrijemeodjave, convert(varchar(20), b.vrijemeprijave, 113) as vrijemeprijave,
CASE WHEN DATEPART(WEEKDAY, b.vrijemeprijave) in (1,7) then 0 else (CASE WHEN (DATEDIFF(SECOND, b.vrijemeprijave, a.vrijemeodjave) / 3600) > 8 THEN 8 ELSE(DATEDIFF(SECOND, b.vrijemeprijave, a.vrijemeodjave) / 3600) END) end    AS radni_sati,
CASE WHEN DATEPART(WEEKDAY, a.vrijemeodjave) in (1,7) then (DATEDIFF(SECOND, b.vrijemeprijave, a.vrijemeodjave) / 3600) else(case when(DATEDIFF(SECOND, b.vrijemeprijave, a.vrijemeodjave) / 3600) > 8  then ((DATEDIFF(SECOND, b.vrijemeprijave, a.vrijemeodjave) / 3600)-8) ELSE NULL END) end AS prekovremeni
FROM(SELECT IdPrijava, redni_broj, radnik, vrijemeodjave, ROW_Number() OVER(Partition By IdPrijava ORDER BY vrijemeprijave) as RowNum
FROM dbo.prijava_radnika) a INNER JOIN(SELECT IdPrijava, redni_broj, radnik, vrijemeprijave, (ROW_Number() OVER(Partition By IdPrijava ORDER BY vrijemeprijave) - 1) as RowNumMinusOne FROM dbo.prijava_radnika) b ON a.IdPrijava = b.IdPrijava where 1 = 1

Group by Name and sum column radnisati and prekovremeni sati