To delete a working time in day view, click on 'change' under the day where said working time is planned.
Use the dropdown list of the employee and choose the upper option (= empty). Don't forget to save.
2. To delete a working time in week view, drag the working time to the bin icon (option 1). You can also delete one person's working hours of a whole week by clicking the X (option 2).
Information on changing a working time in this article.