Extension of one house

We have a house of briks of around 70m2 with basement and 2 (info fjernet) would like to extend it with 80m2, only on the ground floor, no basement, no second floor. We need someone authorised to be able to apply to kommune for that and that can also have the "ansvarsrett", to be responsable with the construction. The job we can do it ourseves. We need a fix price, not hourly price. You can contact us anytime for a free inspection.