Hello
You have two possibilities :
I.
- users X are in group 1.
- In this group you have 3 projects created by users x.
- users y are in group 2
- Group 1 gives access in ProjectManager to read of Group 2=users y
II.
- User manager creates a project or project.
- In this project you have project members. Each member has a role.
- Project Manager = coordinator = full access
- Project member = developer = read + add
- Project partner = other users = read
Best Regards
Aleksandar