Is the repentance of one who has committed immoral acts (homosexuality and fornication) multiple times accepted, given that he is wondering how to atone for his sins and whether he will be forgiven, or if he is among the cursed whose testimony is not accepted, especially after having repented with sincere repentance?

The sin you committed is grave, but Allah forgives whoever repents, no matter how great or immense the sin, for Allah Almighty said: "Say, 'O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allah. Indeed, Allah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful.'" The obligation is sincere repentance, and it is recommended to increase good deeds because good deeds erase bad deeds. As long as you have reached this stage, it is a sign that your matter is heading towards good, and it is sufficient for the truly repentant that he is beloved by Allah. You must conceal yourself and not inform anyone about what happened.