The new INSTAR web interface for your IP camera detects automatically what default language your web browser is using. By default, the web interface will be loaded in the language which is used by your web browser. You can also click System / Language for 1080p cameras, or Software / Language on the left side navigation of your 720p camera, in order to select the language, you would like to use.
Go to System / Language and choose the language you want to load the user interface in.
Go to Software / Language ...
... and choose the language you want to load the user interface in.