Can the sin of kissing between an engaged couple be atoned for after the problems between them have multiplied?

You both must repent sincerely and conceal what has occurred, for the expiation of what happened is sincere repentance and righteous deeds. Problems can be a punishment for disobedience, and if the suitor is righteous and has repented, he should not be forsaken, because "one who repents from sin is like one who has no sin."