How can I see all my tasks on one page?

You have several options on Canvas WU to get a cross-course overview of all tasks (To-Dos):

Open the Dashboard. On the right you will see all the tasks under the menu point To Do.
Select the List view in the Dashboard (take a look at: What do I see on the Dashboard?).
Open the Calendar and select Week, Month or (today's) Agenda.

You can also create your own To-Dos and assign them to a specific course if required. Click on the + in the list view of the Dashboard to do so. Those To-Dos will then appear as regular To-Dos in all To-Do lists.

NOTE 1: If you click the X next to a to-do in the To-Do list, it will be completely removed from the To-Do list. From then on you can access the to-do only via the calendar, via the list view of the dashboard or directly in the respective course menu (e.g. assignments).

NOTE 2: Usually, only assessed tasks are displayed in the To-Do list. In a course, however, there may be other (mandatory) tasks that do not appear here, unless teachers have marked them as mandatory tasks in the course.

NOTE 3: If you have missed the due date of a to-do, it will be marked as “missing”. In the list view of the dashboard you will find an alert menu with all missing to-dos. If you click on the X next to a missing to-do it will move to the “Dismissed” section.