If you are struggling to agree with your neighbour, regarding the fence between your properties, then the Fences Act can be used to quench any disputes. The law applies to most landowners in Denmark, with the exception of the Copenhagen Municipality.
Other neighbourly can conflicts arise, for example, when the neighbour trespasses on your property. Building lines and height rules can also be reasons for conflict. There are a number of provisions that can limit your right, to decide for yourself, how high you can to build on your property.
the number of years it has been occurring is important for whether they can win the claim. If it has been going on for so many years, that an established right has arisen, the assessment may be that your neighbour can continue with his behaviour.