please explain

What chapter are you on? I don't want to accidentally give any spoilers

Oh I read everything already ! But still am confused

Okay, so basically the FL is in love with her "twin brother" who's actually a demon that was born as a product of his mother making a wish to a devil for a son, so basically he's like a devil baby. The FL has been kept in confinement for majority of her life because of her mother who noticed her attraction to her brother that she had from a young age, for this reason Annette is quite ill informed when it comes to basic world knowledge, and she craves freedom. Because she's grown up this way, her father regards her as useless, so his only gain from her would be to give her off to someone in marriage, which he did when she was younger (like 14 or something). After the experience of losing her virginity at a young age in front of an audience and having her husband slaughtered after their first night, she became traumatized by her first marriage. It's been a few years and her father has decided it's about time to attempt to give her away for marriage again, and naturally she doesn't want that, so remembering her mother's words she went to the dungeon or whatever and made a wish to get out of the marriage. After making the wish she witnessed her "brother" turning into a devil, and he raped her. After this, she and Johan continue to have an illicit relationship between the two of them until a rich old man from her mother's country wanted to marry Annette, after which she's taken there to marry him and she gets a taste of freedom. Although, it's not long before she realises she's not in a better situation there than back at home. Her husband beats her for the slightest things and her "step-son" wants her to kill his father for him, and now Johan has come to save her from her predicament.
There's a lot of backstory going on where they show how Johan came to be and the truth behind their younger brother's birth, but that's not really part of the main plot. So, just focus on the romance and the demon part.
Kretschmann, the person whose name she mentions in her retelling of these events is like the devil's advocate or something that came out in a previous chapter when her mom made a wish to the devil.

It's pretty long, but I hope it helps