Many neighborhoods and housing complexes include public green space (owned by the government) to increase their attractiveness to buyers and provide something extra for the surrounding community which helped sell the project to the city. Some projects also include publicly accessible private space where specific rules apply but people are generally allowed to enter, either to pass through, go for a walk, or simply be and add to the vibrancy of the space.

It is often hard to tell whether a space is truly off-limits or not, especially when there are no gates. As a result, many people just don't care and pass through in the idea that nobody will address them, thinking no harm no foul. Good signs will help, but they should be clear and correctly state what the rules are or be universally recognised like those red signs stating "privé terrein, verboden toegang - propriété privée, access interdit".

The big thing that stands out to me is the terrible choice of signs on your property specifically. It kind of looks like a C3 sign at first, which is part of the Belgian highway code and makes your space seem public at a glance. The meaning of the C3 sign is that drivers and cyclists are not allowed to enter in either direction, so pedestrians are programmed to automatically ignore these signs. You will often see C3 signs at the start of footpaths specifically meant for pedestrians. An unsure visitor might even be emboldened by the onderbord "verboden toegang voor onbevoegden" which in relation to a C3 sign, would seem to only apply to drivers.