Comedy(?) Manhwa where the FL is reincarnated into the body of the ex-wife of the ML who he kills

Question

The (new)FL dies and is reincarnated into the body of the ex-wife of the ML, who based on the novel(?) she had read before. He killed her before the start of the actual story (the OG!Novel). The thing that set this one apart was that the ML had always loved his ¨wife¨, even though she hates him. She constantly uses his money for her greed and cheats on him openly. The reason why she hates him is because he is a bastard/illegitimate(idk which one) and her pride was hurt. She was first engaged to his brother but he died and she then got engaged to the ML.

The ML is at first skeptical about the FL new affection (she tries to be nice to him so that he doesn't kill her later on) but eventually he comes to understand that she does like him in some way (the FL is reallllly slow in finding out her actual feeling for him.) I did not get to the part where it´s explained why he killed her in the OG!Novel, but it is hinted that he ¨had¨ to. I also never read the part where the OG!FL shows up but I do remember one scene from the novel.

Basically the ML has to fight in this tournament but it´s kinda a set up by the prince(?) (I don´t remember if it was a price or king) but basically he would have to go up against the prince: which was a lose lose situation for him since if he hurt the prince he would be in trouble but he also would look weak if he lost (or something like that). I do remember that he also killed a lot of the FL´s old past lovers (she cheated a LOT) He wins (duh) and then like the FL had to have a horse race with the Prince´s wife(PW) and she used a lot of magic to bring the PW old horse to give her more confidence and get on her good side. But she used too much magic and she ended up passing out which made the ML go into a panic.

That´s all I can basically remember about the story. :,) please help, I would love to finish the novel.

Edit: I have finally found the novel, if anyone is interested it´s called ¨How to Divorce the Male Lead¨

Answer 1

As stated in an edit to the question, this is How to Divorce the Male Lead, a webnovel. There is no manga adaptation, but there is a promotional oneshot.

On a normal day like any other, Duchess Juliana Auburn woke up from a dream. No, rather, it is I, “Lee Sian,” who remembered my past life.

Juliana Auburn was a character in a novel who did nothing but badmouth and find fault with her husband, his friends, and her own father who had forced her to marry an illegitimate man.

According to a spoiler comment that I read, she will be killed at the start of the novel.

“Why did I only remember everything now after I’ve already done all of those bad things to the male lead?!”

In order to avoid the novel’s “bad ending,” Juliana plans to divorce her husband, Evan, the male lead….

The promotional oneshot does include a scene with her trying to divorce the male lead via expensive purchases and gifts from her lovers.