I did several engineering internships as well 15 years ago. I also faced the same issue of low fluency when first meeting new people and starting a job. After a couple weeks, things got better, I got more comfortable and everyone found a way to communicate. I kept working on my fluency, used any technique that would work, and worked through it. Don’t give up. Even today I met my manager in person for the first time since starting a new job during Covid. I had several big blocks and disfluencies, but got full support from my manager. They hired you for what you have to offer, and most professional employers will want to make it work.