Tips for the Asean scholar interview?

Hello! I just received my email for the invitation to the interview and I am so so happy, until i realised that my english is mediocre and i still struggle a lot with stutters and having a lot of “uhhh” and “um”! To any Asean Scholars out there or anyone What should I do? How do i prepare? Were the judges scary ? Thank you very much for any information!!!