A simple search engine search should come up with some general sense of how to do something like this. How you do it with graphics and such is up to you. I will post a YouTube video at the bottom that came up as a top result from searching for Godot dialog addons.
This isn't entirely what you are looking for, but is generally what you are looking for to help you get something going. I know there are modules or assets out there that people have worked on that are like this as well. I will leave the rest of the research up to you.
Godot Dialog System Added