Help with an entity-relationship diagram re Manager entity type and its relationships In the below ER diagram: 


A manager can have many Users but a User can only have 1 Manager
A Manager must be able to assign multiple users to multiple courses


Are the manager relationships correct?
One issue with this design is allowing for a user to have more than one course at a time. A way to work this is to have a join table between the User table and the Courses table, with only three columns: Join_id, Course_id, User_id. The relationship between users and managers looks good to me, with many users being assigned only one manager each.
Regarding one of the comments; adding to the Course_Assigned table a few fields that include a session_id, start_date, and end_date could be used to directly connect a user to a particular session.