Nonlocally modified gravity and numerical relativity in cosmology As I am a newcomer at ICS, I propose to briefly describe the spectrum of my competences by summarising my previous and current works. I will then mostly focus on yet my two main research subjects that lie in modified gravity and numerical relativity applied to cosmology. First, I will provide details on observational constraints and Bayesian model selection studies in a particular class of modified gravity theories, i.e. nonlocal gravity, where complementary cosmological data from probes such as the cosmic microwave background, supernovae, galaxy clustering but also future gravitational waves interferometers are considered. In a second part, I will describe my research in numerical relativity where we aim to solve for the evolution of dust bodies within the context of numerical relativity, that is, where the dynamics of gravity is resolved by using full (i.e. non-perturbed) General Relativity.