How can one atone for the sin of abandoning prayer due to laziness, if they started praying at the age of 15 and wish to repent?

Prayer holds immense significance in Islam; it is the second pillar after the two declarations of faith (Shahadatayn) and the first of a servant's deeds to be examined. Whoever observes it will succeed, and whoever neglects it will fail. Severe warnings have been established for those who abandon it, such as Allah's saying: "There succeeded them later generations who neglected prayers and pursued desires; so they are going to meet evil" and "So woe to those who pray, [but] who are heedless of their prayer." Prayer becomes obligatory upon reaching puberty. It is imperative to maintain it and to make up all missed prayers after confirming puberty. If you cannot ascertain the exact number, continue making up prayers until you are reasonably certain that you have cleared your responsibility. Some scholars hold that one who intentionally abandoned prayer does not make it up but rather repents and performs many supererogatory prayers. However, the obligation to make up missed prayers is the view of the majority of scholars, and it is closer to caution in religious matters.