Problem in adding new language to Fiori Launchpad

Hi.

I have added new language (Z6) to sap Fiori launchpad. ( add in tcode: 'I18N', then add it in tcode: 'SMLT' ).

In tcode: 'SMLT' I set supplementation language to 'ENGLISH'.

when I log in to Fiori Portal with new language, I see a problem:

Labels and error messages are shown in German!

For example 'First Name' is shown 'Vorname'.

I had done it in other systems as well, but I didn't face to this problem.please help me to solve this problem.