You have to update your record rules like this:

1️⃣ Rule: Employees can only view tasks related to their assigned projects: 
Model -  project.task
Domain - ['|', ('project_id.user_id', '=', user.id), ('project_id.privacy_visibility', '!=', 'employees')]
Permission - Read


2️⃣Rule: Employees should not be able to create, edit, or delete projects:
Model - project.project
Domain - []
Permission - Read


3️⃣ Rule: Employees can edit their assigned tasks but cannot create or delete tasks:
Model - project.task
Domain - [('user_id', '=', user.id)]
Permission - Read, Write