Hi all.
No panic and insulting, ibad ;) Just go to assist --> settings and mark the option as spotted by the red arrow in the picture and you can edit your brightness, gamma and contrast in game as before. I had the same promblem, when "advance FS" was marked...
(https://aao25.com/forum/proxy.php?request=http%3A%2F%2Fwww.maenner-der-ersten-stunde.de%2Fdownloads%2Faao25_settings_01.jpg&hash=f2fc7b32cf871ba5e28704e4a6e1d9a4)
Regards
Graf