Neutron star mergers represent a unique opportunity to investigate fundamental physics in regimes which are inaccessible in Earth-based laboratories. In this report we present two projects aimed at furthering our understanding of these systems. Firstly, we present a novel implementation of a neutrino transport scheme which will allow us to incorporate weak interactions self-consistently in future simulations. Secondly, we present high resolution simulations aimed at understanding the impact of the initial magnetic-field topology on the exponential amplification in the postmerger phase of neutron star mergers. We also give a brief introduction to the numerical techniques used to model these scenarios and summarise their performance on the HAWK supercomputer system.