I have maybe some advice hut nonetheless but i am so proud fellow gamer your in a PROFESSIONAL ENVIRONMENT and you MOVED COUNTRIES!! Boyyy you got life going right don't let your own self make you more stressed, Im not saying that you shouldn't be nervous at all but it seems like they hired you for a reason and i doubt you stuttering will change that after all , your boss already know so nothing wrong with giving a friendly reminder that you might need a bit more time talking idk if you have it but i tend to overthink everything even thinking about going to the store is nerve racking (but going isnt ahah) enough of my rant but dont stress you got this man seriously