What should I do, as I have betrayed my husband with another person due to reasons related to my husband's neglect of me, and I found in this person what I did not find in my husband, and he wants to marry me?

The obligation is to initiate sincere repentance, sever ties with the other person, and turn to the husband by improving treatment, beautifying oneself for him, being frank with him, overlooking what can be overlooked of his shortcomings, and guarding against the temptations of human and jinn devils. Inciting a wife against her husband is one of the gravest major sins.