How can someone whom God Almighty has cursed and expelled from His mercy believe, when an infidel has entered Islam after God has cursed him?

Lana (cursing) is expulsion and banishment from the mercy of Allah. If it is directed at a disbeliever (kafir), it means expulsion from His mercy and entry into Hellfire if they die upon disbelief. However, if it is directed at a Muslim, it means being prevented from entering Paradise at first, unless Allah pardons them. Cursing is only confirmed for a disbeliever if they die upon their disbelief; if they repent before their death, the curse is removed from them. It is not permissible to curse a specific disbeliever unless there is a textual proof for cursing them, such as Iblis, or if their death upon disbelief is known, because a living disbeliever may embrace Islam.