Datbase Diagram

Hi All.

I have problem with connecting the 4 tables:

table1 - Functions (FunctionID, FunctionName, ManagerID)
table2 - Teams (TeamID, TeamName, FunctionID, ManagerID)
table3 - Users(UserID, FName, LName, Email, TeamID)
table4 - Managesr(ManagerID, UserID)

Different Teams can have different functions so the relation I made is:
Teams oo---> Functions

Teams and Functions have their managers so the relations will be:
Functions oo--> Managers
Teams oo--> Managers

Users are assigned to team:
Users oo--> Teams

Managers can aslo be User:
Managers oo--> Users

I know this relations are not correct because I am not able to insert data to this tables. Tables are "looped".

Any suggestions regarding to my problem?
How should I create the tables?

Thank You in advance for You help.

I am thinking about adding 3 more columns to Users table (IsManager, TeamManager, FunctionManager) and remove Manager column from Teams and Functions tables.
TeamManager column will keep id of team which user is manager, and FunctionManager will keep id of function which user is manager.

But my question is what if one user is manager of many teams and many functions?
I will have to put many waluest to the TeamManager and FunctionManager and I dont think it's good idea.