I had to convert the date/time to US from euro to get this to work using the date/time in the corresponding cells.

In A2 I used =SUM(B1-A1)
In A3 I used =SUM(D1-C1)
In A4 I used =SUM(A2,A3)

A2-A4 I formatted cells custom HH:MM:SS

A1: 05:05:36
B1: 01:02:32
C1: 06:08:08

Sorry, didn't see that you wanted to exclude weekends. Found this in another thread that mau point you in the right direction:

=IF(COUNTIF(HOLIDAYS!$C$4:$C$14,A5),"h",IF(OR(F5=" Sat",F5="Sun")," ",SUMPRODUCT(--(WEEKDAY(A5+1-ROW(INDIRECT("1:"&DAY(A5))),2)<6),--ISNA(MATCH(A5+1-ROW(INDIRECT("1:"&DAY(A5))),HOLIDAYS!$C$4:HOLIDAYS !$C$14,0))))
Hope this helps, If it's acting odd, try switching to US Dates