How can one get rid of the feelings of guilt and fear of the torment of the grave after repentance, commitment, and memorizing the Qur’an, especially after committing previous sins related to touching [the opposite sex] and masturbation?

Congratulate the questioner on the blessing of repentance, and recommend attending scholarly gatherings, associating with the righteous, being wary of anything that leads back to sins, having a good opinion of Allah, and not paying attention to the whispers of Satan that cause despair of Allah’s mercy, for the one who repents from a sin is like one who has no sin.