Installing Drupal

Hello,
I bought an update from my original Drupal 7 theme to Drupal 8.7.6 to modify my existing Naturopathy site.
Question 1:
The problem after a test installation of my Drupal 8.6.2 theme by going into 'Status report' I have the message 'WEBFORM: EXTERNAL LIBRARIES 22 libraries (0 installed; 4 excluded; 18 CDN)'
I downloaded and unzipped the missing libraries and uploaded them with FileZilla in the directories in: sites / all / libraries /
/ Choices
/ckeditor.autogrow etc.

I have spent hours doing web searches and found several proposed solutions, but none have seemed to make any difference in my situation.

Long story short: I am a newbie Drupal developer looking to land a project to revamp a static WordPress site in Drupal. The project has a pretty big scope (CMS, media center, Role-based login, API integrations, ECommerce, Microsites) so I may very well be in over my head for this project, but I am also excited for the opportunity and the chance to expand my skill set by learning Drupal!

Hello there. 

Newcomming to Drupal community, I have chosen Drupal (8.7.5) as the base for getting into deploying web solutions based on CMS for further projects, and really would like to understand architecture of this platform. What is the best way for making a local server on Mac for further different web development?

I currently have a Drupal 7 site (https://thehappyscientist.com/) that has over 1800 pages, makes heavy use of the Views module (over 300 views), and has a large, subscriber database.  I need to move to Drupal 8, and am trying to decide between trying to migrate the site to D8, or starting with a blank D8 site, and rebuilding the site to clean it up and remove unused fields, etc.