Hello everybody,
How can you make someone speak in a game or a dialogue?
Thanks!

dialogue/conversation can be simple or complex, there's a number of resources on this type of stuff.

there's the quest doc site too, along with a tutorial, and guides as well:

ht.tp://docs.textadventures.co.uk/quest/
ht.tp://docs.textadventures.co.uk/quest/#Tutorial
ht.tp://docs.textadventures.co.uk/quest/#Howto
ht.tp://docs.textadventures.co.uk/quest/#Npcs

You can also see the 'libraries and code samples' forum board section, and look for such threads/guides/libraries/coding on this type of stuff:

ht.tp://textadventures.co.uk/forum/samples

and there's also Pixie's github page too:

ht.tps://github.com/ThePix/quest
ht.tps://github.com/ThePix/quest/wiki

(remove the dot/period in the 'ht.tps / ht.tp' for it to work within the url)