Need an estimate for upgrading Drenering for a house in Asker-

I plan to buy a new house in Asker but there is a serious problem with humidity in the basement. Apparently, Drainage around the house is not working properly. i need to upgrade drainage (Drenering) before i can move in. i am trying to understand how much it will cost if i want to fix drainage for this house according to the latest requirement (ca 50 m)