The default language is controlled via the entry in
the process unit.
Open the window System -> Configuration -> Process Unit. Call up the process unit for which you
would like to define the default language by entering the number of the Installation and the Process Unit.
Overwrite the language with the number of the language
you would like to define as the default language. If you do not know the number
you can also select the data record via the Search
Function.
Save your entries. The changes will only become
effective after you stopped the process unit (click) and restarted it.