Once you hover over a task with your mouse, some options appear. Those include a comment icon, a +1, a +7 and a trash bin icon.
The numbers +1 and +7 move the task one or seven days ahead. The trash bin is obviously to delete the task, while you can edit the task with a click right onto what you'd like to edit. Click the text, the badge (Call in this case) or the scheduled time in order to edit it. You can also change the responsibility of the task by clicking on the assigned user or his acronym (SS for Sven Sester in this case).