The KM3NeT/ORCA is a next-generation neutrino detector, currently under construction in the Mediterranean Sea; the final detector geometry is optimized in such a way as to reach the maximum sensitivity to the measurement of the neutrino mass ordering (NMO), by studying the oscillations of the atmospheric neutrino flux passing through the Earth. Due to the detector modular structure, the first neutrino oscillation analysis has been already delivered with only 6 Detection Units (ORCA6), over the 115 expected in the final geometry, and 354.6 days of stable data taking. In this talk, results from the first atmospheric neutrino oscillation measurement in the ORCA6 detector will be reported; a particular focus will be dedicated to the event reconstruction and classification for improving the ORCA6 sensitivity after almost two years of data taking. Finally, sensitivity studies on the NMO measurement, atmospheric neutrino oscillation parameters, and tau appearance, in the full detector, will be presented.
