Hi flimflam,
You are welcome. I can’t tell you what the process is with your staging environment, but I’m sure your hoster has documentation for it.
My process is as follows:
I usually create my sites in a local installation, whether it’s an entirely new site or an existing site. For this, I typically use https://localwp.com (alternative: https://kinsta.com/devkinsta).
If it’s an already existing site, I export the posts, custom posts, pages, etc., either directly or using https://www.wpallimport.com if it’s a bit more complex (custom fields, etc.).
Then I prepare my local installation, create or import the Custom Field groups, etc. and import everything one by one using WPAllImport. This way, I make sure the new site is as “clean” as possible. In between, of course, I make backups before each critical step.
When the site is ready, I upload the entire local installation to the server (into a new, empty folder). After that, I update the wp-config and the database (swap the local URL for the actual URL - you can theoretically already do this step locally with a plugin, but I prefer to keep the local one as a test site ). And the last step is to change the domain to the new folder. That’s it in general.
As I said, how that works for you with your staging environment: I have no idea 
The local environment’s significant advantage is that many things are much faster, be it installing plugins, creating and importing backups (which also works directly from LocalWP).
Greetings,
timmse