The only thing I do that has ever come close to helping in this kind of situation is to sing I'm the car loudly and proudly the whole way there. Songs you know well, maybe songs in that language that you know well. It only holds for me about 15min but it helps me get set up. I do not sing in front of others and have no talent whatsoever. I hate focusing on my breath when talking it does not help and usually makes me lock up anyway. When singing a song poorly and loudly alone in my car.....I know I don't have to focus on my breath or the sound of my voice and it's basically a no pressure situation. This also helps me work up endorphins and feelings like " If they don't like me that's their problem" even if the stakes are high I feel like if I keep pressuring myself it's just going to make me clam right up speechless.