In our company we work 8,8 hours per day. Can I set the working hours from 7:30 to 11:30 and 13:00 to 17:18?
You can edit the work day - go to the Project Inspector, scroll down to the bottom edit the the day to 8.8 hours.
@dsakuma Information about editing the number of hours in your work day, like @Nick mentioned, is available here:
You may also want to update your project work hours in Calendar view:
https://support.omnigroup.com/documentation/omniplan/mac/3.9/en/working-in-calendar-view/
Hope this helps!