As a live service game, you cannot save your game. You don’t have to. The server handles your data such that you can stop anywhere and continue from where you left off later. Unless you're in a domain, in which case you'll be booted out of the instance. Unfortunately, this also means dialogue decisions are final, and you'll only be able to see the different branches through transcriptions. Mostly, dialogue differences are minimal, so you're not going to miss much anyway.