How can an unbeliever become dust in his grave and then be brought back and beaten, which is something we do not see, considering that it is the soul that is tormented and connected to the body like a sleeping person?

According to the Sunnis, the torment of the grave afflicts both the soul and the body together. Our inability to see it is not an issue, as it pertains to unseen matters, and some animals can hear it, unlike us. Prophetic traditions indicate that the deceased hears the sound of his companions' footsteps, and that the disbeliever or hypocrite is struck with an iron hammer, emitting a scream that is heard by those nearby, except for humans and jinn. Belief in the Last Day includes belief in the trial, torment, and bliss of the grave. It is obligatory to believe in this without delving into its precise nature.