The elucidation of the electronic and structural transformations that a chemical system undergoes after light-irradiation is of fundamental importance for refining and optimizing new functional molecules and materials. A proper understanding of these processes is possible only through a synergistic combination of theoretical and experimental research. The field of ultrafast spectroscopy has been revolutionized by the ability to produce ultrashort, high-brightness photon pulses with free-electron lasers (FEL). New light sources generate data of unprecedented quality, but to fully exploit their potential, experimental data need to be accurately interpreted. This in turn requires advanced theory and sophisticated calculations. To achieve a better understanding of photoinduced processes in molecules, the proposed project integrates nonadiabatic molecular dynamics, theoretical photoelectron spectroscopy and cutting-edge applications. The specific goals of the project are (i) to develop and implement advances mixed quantum-classical and semiclassical methods for nonadiabatic dynamics, (ii) to extend and improve the Zagreb surface hopping code for nonadiabatic molecular dynamics simulations and analysis ; (ii) to implement efficient protocols for the computation of time-resolved photoelectron spectroscopy signals, including valence and core-level photoelectron spectroscopy, photoelectron circular dichroism and photoelectron photoion coincidence spectroscopy; and (iv) to apply these methods to study challenging molecular systems of atmospheric, astrochemical and biological interest. The results of our simulations will be used to interpret state-of-the-art experiments, which will be performed at the FERMI and European XFEL.