The programme itself is in English*. All communication, presentations, and feedback will be in English. However, if you want to first write your paper in your native language, you can do so. You will then be able to translate the paper into English, or aim for your local journal. But keep in mind that we cannot answer questions or give any feedback on any papers not written in English.
* I also have the same programme in Russian, and am planning to start Spanish next year. If you want to switch to the Russian programme, write an email to firstname.lastname@example.org
or directly to me on Telegram @LiubovAcademio