Magnetotellurics (MT) is a passive geophysical method that measures variations of the Earth's natural electric and magnetic fields. Magnetic field time series are measured in three orthogonal components (x, y, z) using induction coils, while electric field time series are measured in two orthogonal components (x, y) using pairs of electrodes. Information about the electrical resistivity distribution in the subsurface is obtained by processing the measured time series. This processing is typically conducted using commercial software. However, commercial software licenses are often expensive and cannot be modified, making them unsuitable for academic use. The objective of this thesis is to find an open-source workflow for MT time series processing suitable for teaching and research activities at the TU Wien. For this purpose, I evaluate different open source processing codes, their advantages and limitations.  In this regard, the thesis is composed of three main sections: (1) literature research on the available open-source algorithms (2) the use and evaluation of the different libraries and the comparison of the obtained results with a commercial software, and (3) collection, processing and interpretation of exemplary data sets.To illustrate the methodology for the visualization and processing of the data, MT soundings were collected between 2022 and 2024 at three different locations in Austria: the Neusiedler See-Seewinkel National Park, the Hydrological Open-Air Laboratory (HOAL) in Petzenkirchen and the Hochschwab Massif. First, I investigate comparative MT soundings at Seewinkel, a site with negligible infrastructure, and HOAL, an urban environment, to identify and understand the sources of anthropogenic noise. Second, I analyze natural signal variations in the AMT deadband during day and night to assess their influence on data quality. Third, I apply the proposed workflow to four soundings at Hochschwab to determine the resistivity of the of the subsurface to a depth of ca. 3km, towards the delineation of the depth to the water table.The results highlight the importance of examining raw MT data in both the time and frequency domain to identify and understand the sources of noise, outliers and erroneous measurements. In this regard, the thesis also permitted to improve the protocols for the field work towards the collection of MT with higher quality. Anthropogenic noise significantly affects MT data quality and the interpretation of results.  Notch filtering of powerline (50Hz) and railway (16.7Hz) signals and their harmonics, as well as coherency thresholding significantly improve impedance estimation.For one exemplary MT sounding collected at the Hochschwab site, numerical models were tested using forward solver implemented in the frame of this thesis. The water table was estimated at a depth of approximately 1200 m, with an aquifer resistivity of 300–400 Ωm.  These results demonstrate the applicability of the MT method and the proposed open-source processing workflow for groundwater exploration. However, further analyses, including dimensionality analysis, topography correction and inversion, are required to fully understand the groundwater geometry and to accurately estimate the depth of the groundwater table.