It's maybe simple, but I just can't find answers here. How can I update an ID value. Do I need to remove the old object and make a fresh new one and save it to the database or I missed something here?

How can I change the identifier value of an existing instance (ie. the primary key)
It is part of the definition of a primary key that it is not only unique, but also constant throughout the life of the row. Hibernate does not, and should not, support changing identifier values.