What is the way for a 16-year-old youth who commits sins and fears that Allah will not accept his repentance to repent?

There is no happiness for a servant except by turning to Allah, fulfilling His commands, and avoiding His prohibitions. So, adhere steadfastly to Allah's law and strive sincerely against your lower self, so that Allah may avert the plots of Satan from you and help you against your soul that incites evil. Beware of thinking ill of Allah. Reflect often on death and what comes after it. Avoid bad company. And ask Allah for guidance.