The first thing to know is that in Beesbusy, as long as you have not shared a project, it, as well as all the tasks it includes, remain only visible to you.
If you need to keep a project and its tasks invisible to other members, but still want to assign tasks to members to create and display a realistic schedule, you can share the project with these members and give them "No Access" rights. They will not receive any notifications about the project, will not be able to access it, the project will not appear in their project list, and the tasks assigned to them will not be visible to them either.
For more information, see the article on setting up access rights.
If you want to hide certain tasks for some of the members having access to the project, you can make tasks confidential: only the project administrators and members assigned to the task will be able to see this confidential task.
For more information, see the article dedicated to confidential tasks.