Deleting the config folder solved the problem! The config file was newly created and is no longer empty. My settings stay the same now after each restart. Thanks a bunch!
Posting the log file is no longer needed anymore ...
recently I bought factorio over steam and started playing it. Now I noticed that every time I start the game it'll open in windowed mode. After changing the settings to fullscreen they're being set back to default as soon as I close the game and start it again. The other settings are ...