Hi Roland,
Each service has it's own branding options, and also Administrator overrides depending on how large the account is.
GoToMeeting Logos can also be managed online, through the settings area: https://support.logmeininc.com/gotomeeting/help/add-logos-and-branding-g2m550006
At this time, the email services of GoToWebinar and GoToTraining only support one language at a time. I apologize if this inconveniences you in some way.