Thanks to everyone I have managed to perform what I needed. The solution is a combination of the two articles provided:
@rorycb with How to migrate quickly to separate web and data containers → which helped me to understand how to manage discourse with separated containers for each structure (but it does not have the proper information for a clean installation)
@Falco with Running Discourse with a separate PostgreSQL server → which helped me to understand how to generate images and separate with the previous information to create a fresh installation
And this third link How to set up an internal team forum in half a day using Discourse → which helped me to know how to configure some params to generate a proper setup for a Kubernetes cluster.
I post all of this extra info just in case that in the future someone needs this. Thanks again to @rorycb and @Falco 