Often cars are not permitted so you should go there by foot. The most convenient way to get there is to take a taxi. You needn't hesitate to ask the taxi driver, they are used to drive people there. Often they can give you tips and recommendations. A mall offers the widest variety of girls and is relatively cheap.
Malls are legal in Germany and in the Netherlands.
You must be at least 18 years old to go there. In Germany the girls working there are regularly medically examined so the risks to get a disease are relatively low. Of course you must use a condome. I had sex with a prostitute was in Dortmund. I was 17 years old.