If you want to learn ORM, then I recommend that you get Terry's book "Information Modeling and Relational Databases Second Edition". It has lots of examples and exercises so you can use it as a reference and also go through the exercises.
what if i wish to insert a person in my model that should not be able to login and is not a cusomer of a employee say for example a contact then this model fails.
Regarding my example, it is not quite correct to say that "it is the model that fails". A model is just as you define it to meet your requirements.
With ORM you need to be very clear about what you want and then express that in terms of atomic facts.
For example, if you want to have a Person in your database that cannot login, then one solution is to insert an additional subtype between Person and the Customer and Employee Semantic object types (you might call it WebsiteUser) - then change the Person(.id) has WebLogin(.code) to be something like WebsiteUser(.nr) has WebLogin(.code).
the thing i am try to accomplish is that both a employee and customer can share the same login and its not mandatory that they should be able to login and its not mandatory for a person to do a login either.
So the main problem is that i wish to model it right but i do not succeed defining it in NORMA.
You should find it easier if you break down complex statements like this into a set of atomic facts and then model those.