The setting is in: Administration Center > Features > General.
Default language defines what will be the default language of the system. This setting has no effect on the language you use in the eWay-CRM application on your computer (language option in the General tab). Default Language is used mainly for activities generated by the server - e.g. for generation of system journals when a change of an item occurs, or for different email notifications, etc. So, if you have chosen English in eWay-CRM settings and the Czech in global setting Default Language, the language of your eWay-CRM application will still be English, but when you change for example Price on a project, this change will be logged in the system in Czech language.
Click Default language in reports to see the setting options.
Select the language in the field.
When you change the settings, be sure to click Save. For more information, go to Features.