I’m the same, I have a stutter and I have a few other social issues which mean I really struggle to talk at all to people I don’t know, and even sometimes to people I do know, so I often just stay entirely silent and communicate through gestures, head movements, the same sorts “mhm” type noises, and through writing stuff on my phone and holding it up (or for people I know I will often just text them even when I’m next to them)