Marcus, it's possible by custom code modification. I mean that there isn't any setting, for example in admin panel, that you can change to achieve needed results. You need to edit php files. I can not provide you with detailed instructions. All I can just show you the direction. You will need to make changes in following files:
/ow_system_plugins/base/bol/language_service.php file,
/ow_system_plugins/base/components/console_switch_language.php file.
I'll PM you an example.
However you need to remember that all your customizations will be overwritten while next update of the software, so you need to remember them and apply again, or implement the changes via custom plugin.
If you are not familiar with the code modification or plugin development, it would be better for you to find a developer who can help you. You can do it here:
http://www.oxwall.org/market/specialists.