This project aims to apply ab-initio theoretical tools to understand the proximity effect on the electronic, magnetic, and optical properties of 2D materials. In nanotechnology, a 2D heterostructure is a stacking of two or more 2D materials that have different crystal structures and properties. These heterostructures possess unique electronic, magnetic, and optical properties that are not present in individual 2D materials, opening the path for new applications of 2D materials. The Spintronics technique utilizes the spin of electrons in addition to their charge for the purpose of carrying and processing information. The spin transfer torque and spin-orbit torque can be used to manipulate spin in heterostructures made of ferromagnetic materials and nonmagnetic 2D crystals. Moreover, 2D magnetic heterostructures can be used in magnetic recording. Such applications can be achieved by tuning the magnetic anisotropy energy of 2D magnets via the proximity effect. The bandgap can be tuned by stacking different materials together, allowing for the creation of materials with tailored electronic and optical properties. It is possible for 2D junctions to exhibit anisotropic optical properties, which means their optical properties change based on the direction of polarization of light. Having all these applications, a thorough analysis of the magnetic and optical features of 2D heterostructures is vital and the results of these computational studies can benefit both the theoretical and experimental scientific communities to have better insight into the rich physics of heterostructures and propose suitable candidates for experimental applications. For this purpose, we utilize QuantumATK software to create and optimize our heterostructures and to study the transport properties, VASP and YAMBO will be used to perform GW+BSE optical calculations. Magnetic properties and spin dynamics will be studied via RSPt and UppASD codes, respectively. All these codes are massively parallelized and have good scalability. A medium-scale access to UPPMAX is vital to us from two points, firstly, due to the complexity of proximity interactions, many-body approximations, such as GW and BSE, are state-of-the-art approaches that are needed to predict the electronic and optical properties of heterostructures accurately and match experimental results. This accuracy, however, comes with an increase in computational cost. GW+BSE method generally needs parallelization of calculations over thousands of Kpoints and hundreds of bands. Accordingly, HPC resources with MPI and OpenMP parallelization are needed to be able to perform these calculations over many computer nodes. Secondly, our license to QuantumATK software is only functional within the Uppsala University network. Therefore, an UPPMAX allocation is essential to utilize this code.