Will God punish me for the thoughts and doubts that cross my mind about the truth of God's existence, justice, and mercy, and what is the solution to get rid of them and restore the sweetness of faith?

You must stay away from suspicious websites and poisoned ideas that raise doubts, and keep away from the charlatans of this era by closing your ears and eyes to their dubious claims. Do not let doubt pass or settle in your heart, and if it does pass, do not think about it or pay attention to it. Make your heart like "glass" through which doubt passes without affecting it. Beware of associating with atheists and people of falsehood, for their companionship is not befitting for people of faith. If you find whispers within yourself, know that they are from the essence of faith, and do not pay attention to them so that Allah may remove them from you. Seek refuge in Allah from Satan and say, "I believe in Allah and His messengers." To refute doubts about the existence of Allah, look at the perfection of the universe. Regarding divine decree, read: "He is not questioned about what He does, while they will be questioned." Allah has not wronged anyone; He sent messengers and revealed books. Whoever disbelieves after that will be punished for his sin. Children in the West will not be punished unless they reach maturity, are presented with the truth, and then reject it.