Some debug stuff Friends cannot log you out currently, and the login system may change from time to time. So if you want to log out, you need to remove The file /home/user/.config/SfietKonstantin/qfb-mobile.conf The folder /home/user/.local/share/data/SfietKonstantin/qfb-mobile/ Cache management is poorly managed, and might take a lot of space. You can remove it by deleting The folder /home/user/.cache/SfietKonstantin/qfb-mobile/