Is something like that going to work ????

Two classes mapped on two tables only - no join tables . OneToOne - bidirectional and ManyToOne unidirectional relationship
Seminar can have multiple students<Users> ,seminar has one owner, user can be an owner of multiple seminars, user can take part in multiple seminars

Is the mapping going to work
@Entity
public class Seminar {

@Id
@GeneratedValue
private long id;

@OneToOne
private User seminarOwner;
@OneToMany(mappedBy="seminar")
private List<Two> seminarStudents;


private int counting;
}

@Entity
public class Two {

@Id
@GeneratedValue
private long id;

@OneToOne(mappedBy="two")
private Seminar seminar;
}