Is repentance for a sin, with the aim of regaining what one was deprived of due to that sin, considered shirk or haram?

A sincere repentance requires that its motive be seeking Allah's pleasure, not recovering a worldly matter that has been lost. So, whoever repents with the intention of recovering what they missed of this world, their repentance is not sincere. As for someone who regrets and repents with a pure repentance due to the loss of a worldly matter, their repentance is valid. This is because seeking worldly gain through good deeds is a minor form of polytheism (shirk asghar), as Allah Almighty says: "Whoever desires the life of this world and its adornments - We fully repay them for their deeds therein, and they are therein not deprived. Those are the ones for whom there is nothing in the Hereafter but the Fire. And lost is what they did therein, and worthless is what they used to do." And whoever learns knowledge for the sake of Allah, but only desires this world by it, will not find the fragrance of Paradise. However, whoever performs good deeds for Allah hoping for benefits and repelling harms, their action is not considered shirk.