How can one atone for masturbation and other sins after swearing on the Quran not to return to them, and how does one repent from deceiving young people and obtaining financial credit from them, and if it is not possible to reach them to return their rights?

You must repent and offer expiation for each oath you broke. You also need to seek forgiveness from those you wronged, or, if that is not possible, seek Allah's forgiveness for them and supplicate for them. As for material rights, they must be returned to their owners, or, if reaching them is impossible, given as charity on their behalf. We advise you to supplicate, strive against your lower self, abandon sins, and associate with righteous people.