1) you mentioned that you feel selfish talking about yourself. dont. please be you. the last thing he needs is for you to treat him differently because he stutters. just talk about yourself, let him talk about himself. dont fight the flow of the convo. 2) about finishing his sentences- you have to know when you can do it. when the convo is about something you both think/do- yes, enthusiastically finish the sentences. thats normal. but please let him talk when he's arguing something or is being serious. 3) ordering food- if he steps in and seems happy to order- AMAZING! if he seems unsure say " i wanna order this time".