How do I attach event sheet to objects to achieve OOP ?

Is there a way to attach event sheets to object ?

Cause right now objects can have its own variables, that is great, but can it also have and manage its own functions ?

Look into using Families. If you have objects in the same family, you can use events on the family to affect all the objects in that family.

Also look into for each loop, to loop through all the objects and apply events to all of them.