How can one repent from neglecting acts of worship, abandoning prayer, and listening to music, and what is the method for the prayer of repentance and daily supplications, and what are the tips for dealing with the whisperings of Satan?

The Prayer of Repentance is an established Sunnah, and its proof is the Hadith: "There is no servant who commits a sin, then purifies himself well, then stands and prays two units (rak'ahs), then seeks Allah's forgiveness, except that Allah forgives him." The conditions for repentance are: abandoning the sin, regretting it, and resolving not to return to it.

For your steadfastness upon the truth: Befriend righteous girls, strive in supplication for the firmness of your heart, and be keen to learn beneficial knowledge from trustworthy scholars. As for obsessive thoughts (waswasah), repel them by seeking Allah's help, increasing in prayer, reciting the Qur'an, and performing dhikr (remembrance of Allah). Fill your free time with memorizing the Qur'an, seeking Islamic knowledge, and calling to Allah.