The relationship between online and offline activism has been studied intensely, especially with the outbreak of COVID-19 that forced environmental movements to be online. Nowadays, activists can mobilize crowds and create unique self-representation online by using social media, which requires specific knowledge and skills. In our research conducted among the members of the Hungarian Fridays for Future (FFF) movement for 3 years, we aimed to describe these skills gained through online activism. We focused on mapping the connection between offline and online activism using various qualitative methods such as participant observation, interviews, focus groups, and digital ethnography. In order to get a clear image, we put heavy emphasis on the Hungarian context, namely the structure of the public sphere, the politicization of environmental issues, and the general approach toward activism and social movements. Our results show a mutually reinforcing process between online and offline activism in which numerous learned skills exist in parallel, in the frontstage and the backstage. The most essential skills are building the image of a strong online and offline community with explicit values and objectives as the most effective way of attracting youth to be activists; and learning skills to keep boundaries between personal life and activism similarly to adult experiences of keeping work-life balance. Although, the effectiveness of the FFF activists in both spheres is influenced by the segmented and politicized public sphere from which Hungarian youth tend to be excluded.