Per Strapi's docs this is not how Strapi is to be used - https://docs.strapi.io/dev-docs/faq#why-cant-i-create-or-update-content-types-in-productionstaging

You should only ever run Strapi in development mode locally.

Thanks for the reply but I don't find anything in this doc about running it on staging mode to be able to create content.
with "strapi start" command or if I leave the field empty, it will be in production mode and i'm not able to create content.

1. Run Strapi in development mode locally, make the changes, add content, etc.

2. Run Strapi in production mode when on Railway, consume the content, etc.

Thanks a lot. I will try

UPDATE:

it worked.