Are curses really granted? I mean does God take it serious and listen to the one who curses?
This is an interesting question, and ought to be a thread unto itself.
I believe that there is a distinction to be made between a vulgar expletive cried out loud as a knee-jerk reaction in a moment of anger or frustration, and the act of will whereby one deliberately wishes ill to another and expresses this act in words or gestures. This latter act is a mortal sin, depending on the gravity of the ill in question, and the sin is even more grave if this act of will constitutes the final cause of an act of superstitious ritual.
God regards such maledictions insofar as they are a transgression committed against His laws and an injury against His sanctity and justice.
Sometimes, I think, God permits the realization of such maledictions in order to test the virtue of those individuals against whom a curse was pronounced, or in order to manifest the imminent reprobation of the one who pronounced the curse (if he does not repent and repair the damage of his sin). Sometimes the apostate Angels are allowed to interfere when their assistance is sought by the sinner in question for the same purpose. This is to manifest the omnipotence of God, Who can draw greater good from evil and thus punish the demons with the humiliating reminder of their ultimate powerlessness and absurdity.
When it comes to anathemas pronounced by (real) clerics according to the rituals of liturgical books and disiplinary norms (as when a Oecuмenical Council issues an anathema against those who deny a defined doctrine, or the famous anathema pronounced by the Bishop in the rite of the Consecration of Virgins found in the Roman Pontifical), it is an entirely different case. God does indeed regard these necessary maledictions both as a medicinal means to lead the transgressors to penance rather than to well-deserved reprobation, or as a means to manifest His zeal for the integrity and sanctity of Holy Mother Church.