With upcoming missions of the next decade like the James Webb Space Telescope or the European Extremely Large Telescope, properties of exoplanet (outside the solar system) atmospheres might become detectable. Of special interest is the detection of atmospheric signatures indicative of life (biosignatures). However, while these are well-defined for an Earth-like scenario, they might be affected by the exoplanets radiation environment, which varies strongly with the stellar activity. This will be investigated in a cooperation between the Technical University of Berlin, University of Kiel, and KIT. Our responsiblity at KIT is to investigate the impact of varying stellar activity for known M-dwarfs and K-stars on the neutral and ion composition of different types of planetary atmospheres.