Oh, my story is really strange) You can see i have only 3 game in my profile. First GameMaker, second Python, and third is Godot, lol. I'm jumping between engines Unity, Unreal and etc, but now i'm staying with Godot, i'm kinda love it.
I started learning Godot after GameMaker and big path of Python before. So i was comfort with .gd.
You know, it's kinda simple to say. Open docs, read it, and make games, learn other projects and etc. But it's not simple to do, xD.
What about dialogue system i'm not creator of this. Dialogic 2, you can find it on github and add it to godot. I was digging into the code and how it's done. Powerful stuff. You can create your own system, using ui nodes and autoloads. Your scene loads in remote tree where can be another scenes you can use. Like transitions between levels, music player, dialogues. You should check autoloads, it's really interesting.
UPD: Btw, effects on text is bbcode you can use it in reach text label. I didn't know that and spend a lot of time for attempt to create my own system.... A big adivece... always read page of documentation to the end, loool. I just opened information about text, find that i can use color change and didn't go down where was information about text effects like shaking and wave you know.
Thank you for playing and questions, have a nice time learning Godot!