If a Task in your Task List is no longer relevant, first you need to find out why it is there in the first place. Tasks can either be added manually or triggered automatically from a checklist based on the answers you have given.
For tasks triggered automatically, the checklist that triggered the task will be indicated in the 'Why is this in my Task List?' area (as highlighted in red in the screenshot below).
The best way to remove tasks that have been triggered automatically is to update the checklist that triggered the answer. Simply click on the link to the checklist within the 'Why is this in my Task List?' area and review the associated checklist. For more help on completing or reviewing an online checklist, see our guide 'Completing an Online Checklist'.
For tasks which were added manually, these can either be archived/ closed or deleted. Both of these options require administrator permissions so you may need to ask a System Administrator to do this for you.