When you are actually already doing a debate competition, it seems there's little that can be done, dude even normies would be shy away from a debate competition, so kudos for you, but let's see what you can do: At the face value, I can see you are highly intelligent. Have you tested your IQ? Yours must be pretty high, self-awareness is essential for this stuttering kinda thing and it would especially boost your confidence in general cuz in your case I suspect that it's pretty high; I mean at least in the verbal part. That would ofc shape your self-image positively, potentially helping reduce your stuttering. I can also relate to your experience as I stuttered a little bit more in my mother tongue than I do in English. I went to the U.S. for my study and spoke English all the time while being there. Then I went back to my home country, and I found myself speaking almost fluently in my mother tongue, it's now almost comparable to my fluency in English. It seems that I have almost forgotten to stutter in my native language due to not speaking the language for some time while I was in the U.S. My point being is to try to temporarily reduce the frequency of speaking in Greek, if possible. Lastly, I always give this piece of advice to every young stutterer or well stutterers in general. Don't put too much focus on your stuttering instead do sports, music, toastmaster, programming, etc, whatever things you like. Inundate yourself with productive activities that it makes you so busy you forget to worry about your stuttering. Good luck!