Start from the beginning since there are extra scenes in the novel that explains things compared to the webtoon.
I agree with Moon01234, it would be better if you read the novel from the beginning. The events that happened in the last 2 ch of the manhwa happened in the 13th ch of the novel, so you won't have to read that much more if you read from the beginning. The novel is amazing so I really hope you'll read it from the begging, it's worth it.
Here you can find the novel completed, the first 15 chapters you will have to read on another site, but through this link you'll be able to find it.
https://rubymaybetranslations.com/table-of-contents/
Echo has given you the best translated link for the novel. Looks like I'm diving back in the book for the 5th time since the start of the new year.
do anyone know if you read the novel now.. what chaoter will you start.. considering the chapters already read in the manhwa