The official Twitter account for the manga Koi to Uso revealed that the work will resume its final arc on December 5th . It is worth remembering that it will have two different endings, it will therefore have a “marriage route with Misaki” and a “marriage route with Ririna.”
Furthermore, the 12th volume of the manga will be the final volume, and it will be released on January 7th . There will be two different versions of the 12th volume, one for Ririna's ending and one for Misaki's ending.
The Koi to Uso manga took a break after chapter 280, released on April 18th, MangaBox started publishing the manga from the first chapter with a new chapter per day since April 26th.
Finally, it is worth noting that the 11th volume of the manga had already hinted that the work was coming to an end.
Source: ANN