Under the floorboards of my bungalow there is a drop and than soil, is this normal or should it be concrete?

Maybe there is a high water table in your area and a regular foundation was not possible. This is not a concern, this is basically a crawl space like many houses have - either the whole house or may additions are build over a crawl space. The only thing you have to make sure of is that their is enough airflow under there so moisture doesn't build up. On the outside of the house, there should be vents in several places so that air is free to flow under the house. Also, sometimes if moisture is a problem there will be a plastic tarp lining on the soil surface under the house, with bricks or something all around the edges to hold it in place. This is another way to keep moisture from coming up through the ground.