Borexino is a solar neutrino detector based on 280 tons of ultrapure liquid scintillator, located at the Laboratori Nazionali del Gran Sasso, Italy. In more than twelve years of data taking, Borexino completed the spectroscopy of the solar neutrinos emitted from the pp chain reactions. Borexino also measured, for the first time, the solar neutrinos flux from the Carbon-Nitrogen-Oxygen reactions cycle by analyzing the 2016-2020 data, paving the way for a solution to the long-standing solar metallicity problem. Over the past two years, the Borexino collaboration has pursued the improvement of the CNO flux measurement, to obtain further indications about the solar metallicity with a significantly extended dataset, an improved estimation of the 210Bi background and a refined re-evaluation of the Borexino photomultipliers detection efficiency over time. All the crucial aspects related to the improved CNO analysis are explained in this poster.