Editor Application Language

Can you tell me what language I should use when filling up the editor application form?
Should it be English or I can fill it using the language of the category (in my case Bulgarian).
I have applied a week ago and I have used Bulgarian to fill my application.

The application should be written in the same language as the category you are applying for.
One of the things we need to establish is if your knowlegde of the language is enough te become an editor in that category.