How can one repent from embracing and kissing a girl and asking for her pictures, knowing that the relationship with her has been severed, and the repentant person does not feel the sweetness of repentance this time?

The door of repentance is open, and its conditions are: abandoning the sin, resolving not to return to it, and regretting having committed it. If these conditions are met, along with severing ties with the girl, resolving not to repeat the act, and regretting any shortcomings, then your repentance is sound and accepted, God willing. You must frequently seek God's forgiveness, feel deep remorse, and strive to perform good deeds, for "indeed, good deeds do away with evil deeds." Have a good opinion of Allah, for Allah forgives sins no matter how great they are. Turn to Allah and transform your evil deeds into good ones, and stay away from temptation, for "the one who repents from sin is like one who has no sin."