Hi,
did you get to step 5 (import database)? Or do you want to start with a new, empty database? Unfortunately, I don’t know if it’s possible to create a new, empty database with Gramps on the command line since gramps -C "new" complains about a missing input file. Does anyone know? Otherwise, you might have to create it in Gramps desktop and export the XML for the empty database.
You’re asking about the Gramps-webAPI (via Docker?) by @DavidMStraub ?
Don’t confuse users 
Gramps Web is the new name for the web app formed by the web API as backend and Gramps.js as frontend, both of which now live within the Gramps org.