Two-dimensional semiconductors are an ideal platform to study electronic excitations, the excitons, and their dynamics. This is due to the good experimental accessibility of the excitons and the strong exciton binding of electron and hole. The GW+Bethe-Salpeter approach (GW+BSE) has been successful in computing exciton properties in single-layer 2D semiconductors [1], but the application of GW+BSE is challenging for 2D double layers and moiré structures [2]. This is because the large unit cell in these structures contains hundreds to thousands of atoms, resulting in a high computational cost for GW+BSE calculations. In this talk, I will present a low-scaling GW algorithm for 2D materials that potentially allows for the inclusion of more than a thousand atoms in the simulation [3]. The GW algorithm is based on localized basis functions and can handle periodic boundary conditions and the divergence of Coulomb interactions in the Brillouin zone. I will present GW benchmark calculations and I will outline its generalization to BSE and time-dependent variants for the study of exciton dynamics.