Tasks are only shared with team members if they are in shared team list. Your personal tasks are, by default, not shared with your team.
If you want to share a specific task with your team, you will need to add that task to a Shared list.
To be sure that your personal tasks are not shared with anyone else, you can access the list's properties from the main page.
1. Navigate on the left panel and look for the list that you want to access. Hover on the list name and click on the small gear icons on the top right.
2. A menu should open up and you will be presented with options to edit the list. Click on "SHARING" to see who has access to that list.
3. A window will open up showing all the users who currently have access to the list. You can also grant users access to this list through this window by clicking on "Add More People."