The GERDA (GERmanium Detector Array) experiment, located at the Laboratori Nazionali del Gran Sasso, is searching for neutrinoless double beta ($0\nu\beta\beta$) decay of $^{76}$Ge. Since the end of 2015, in Phase II of the experiment, 35 kg of enriched high-purity germanium detectors are operated in liquid argon, that serves as cooling for the detectors as well as active shield against external radiation. The aim is a sensitivity on the $0\nu\beta\beta$ decay half-life larger than $10^{26}$ yr with about 100 kg$\cdot$yr exposure and a background level of about $10^{-3}$ cts/(keV$\cdot$kg$\cdot$yr). An overview of the analysis of the data collected so far is presented with an emphasis on the background rejection techniques and their performance together with the half-life limit.