Drupal 8.x

I have been learning and building my new website with Drupal 8.
As I had a Blogger-built website in place at the website address, I built "mynewsite" in a folder, within a subdirectory, under mysite.com
(I am still learning....) The mynewsite address at present is therefore eg: http://mynewsite.mysite.com/mynewsite
The newsite is now completed and I am ready for the site to go live.
How, please, do I move the complete website and all files and databases, out of the present folder, within the subdirectory and into where it should be - so that the mynewsite's address will simply be http://mysite.com and I appreciate any assistance.

Hi folks

Might be my first post here and I couldn't find some decent information about this so I'll ask it here.
How would you load in an additional css sheet when a used is logged in.

I want to shave as much overhead for the visitor as possible and this is one of them.
Contains some tweaks so the user menu won't interfere with the admin menu's when logged in.

I've got my main css in style.css and an additional one, named style-admin.css.

Tried looking for something like:

Hi everyone,

I'm trying to setup drupal on my webserver using nginx. For this I used the following config file as a start:
https://www.nginx.com/resources/wiki/start/topics/recipes/drupal/
Everything works very well except for one thing:

If i request the page "mydomain.com/", I get the main page as expected.
However if I request "mydomain.com", I get a message saying that the page could not be found.

Hi, I'm a newbie with drupal and I'm trying drupal 8.
If I create a new content type adding a field of type "image" with multiple selection, how I can mark the "principal/default one"?
If I need, for example, to show the main image in a list of items..
Thank you in advance

I found a message in my log file indicating there was a missing module. I would appreciate help understanding this message.
What module is it talking about? Is there a way to remove the need for this module?

I have no experience in this area and so I have many questions. Info I'm finding on the subject seems to either be to simple or too advanced to get a thorough understanding of what a migration like this entails or how managing a drupal site on a server works.

I am on windows 7, my drupal installation (8.2.4) is on Xampp 7.0.13 / PHP 7.0.13 localhost and the databases are MySQL. I've been using phpmyadmin to manage my databases. All I know how to do is export databases as .sql files and import .sql.