Do sins remain for a person who repented from sending a forbidden picture to a fraudulent website that in turn sends his picture to other girls?

As long as you have repented to Allah from this sin, your repentance is accepted, and Allah will erase the effect of this sin from you, because the Prophet, peace and blessings be upon him, said: "The one who repents from sin is like one who has no sin." The dissemination of these pictures against your will does not harm you, for the persistence of the effect of a sin after repentance does not invalidate it.