Hi,

You can set the culture settings for the live site in the Site Manager -> Sites -> edit your site -> culture fields.

for particular user account please go to Administration tab -> Users -> finde your user account and edit it -> here you can see also two drop down lists with culture. Please select certain culture for the Preffered UI culture. you may need to log out and in again to apply this change.

Best Regards,
Juraj Ondrus