Do I have to pay taxes in my home country for my property in Spain?

In both Belgium and the Netherlands, you have obligations.

At Belgium you need to file the foreign cadastral income (KI) return 4 months after purchase. You are not taxed on the KI, but it potentially pushes your other income into a higher bracket (progression bias). Find more information on foreign KI here.

At Netherlands you have to take box 3 into account. Find more information on box 3 and foreign property here.