I’m curious if you are looking for the typewriter effect or the dialogue system because your title asks one thing but your body asks another. I’m going to assume it’s the dialogue system as I think there are a few typewriting effect tutorials already on the internet.
Basically there is a lot of different ways to achieve a dialogue system and there probably are a few good tutorials out there that can show different ways of achieving this. In my personal opinion the easiest way to achieve it is to use Data Assets. Basically each data asset can store a line of dialogue, the character saying that, and anything else you need in a single line of dialogue. Then what you can have in each data asset is a variable that can point to the next data asset.
This is kind of a pain to actually use though if you are creating long dialogues, however, beats going into c++ and using Slate to create a custom editor which is cool but only recommended if you are on a big project and the game is based around dialogue!
What this ends up looking like in game though is that you feed a data asset into some sort of dialogue manager which could be an actor or a subsystem if you have access to c++ and the dialogue manager can manage the displaying of the data inside of the data assets. If you want choices you can make a choices variable. The theology is pretty simple, obviously the implementation is going to be a different.
Hopefully that’s enough to give you a start and hopefully I answered the right question that you were asking.