if you use black magic unfairly will it somehow negatively affect you? or the gods must approve your curse that you want to send to someone for it to work. I don't quite understand
Yes, as the gods know what you do, so they might not help, in the extend they would normaly.
For example: If you give a child a shovel and the child starts hitting other children with it for no reason, you can take the shovel away and punish them. In the future you may refrain from giving said child a item/help.
if you use black magic unfairly will it somehow negatively affect you? or the gods must approve your curse that you want to send to someone for it to work. I don't quite understand
If you ask for Gods' help in making your curse work, but it is unjust, then your help will be denied if it is unjust from the point of view of Divine Ethics and Gods, not just from your point of view.
If you are not asking for Gods help, but you apply a curse and it is unjust, it will work if you are sure it is just. If you are not sure that it is fair, the curse may not work because your uncertainty about fairness can undermine your work.
When you do magic work, you must be sure that your actions are right and correct, but you must see to it that your actions are in accordance with Divine Ethics.
We have a calendar and today specially is a day that you can do curses in this way. Magic is about equilibrium and you have to ask permission to the gods and your protector.
Our actions have to be guided by justice and not emotions.
Have a nice sunday.