Are the ongoing sins still accumulating due to assisting in an foreign movie website that contains bad scenes and blasphemous statements? And will I be held accountable for sins every time someone watches or downloads it, knowing that I have repented, regretted, and distanced myself from this friend?

Undoubtedly, aiding in the spread of evils, such as promoting immorality and blasphemous statements, is among the greatest sins. Whoever repents with a sincere and complete repentance, Allah Almighty accepts his repentance, even if his repentance was from disbelief, for the Prophet, peace and blessings be upon him, said: "The one who repents from sin is like one who has no sin." Part of perfecting repentance is to strive to remove the traces of what one helped spread, to the best of one's ability.