How to use same database for two website but different panel?
You should start from https://www.drupal.org/docs/8/multisite
Drupal supports multisite structure out of the box. You don't need Domain Access module to reach it. 
You may share some db tables among your websites, e. g. content but keep settings (Views, display settings unique). It depends of your purpose. Also you may have shared or unique modules and themes. 
The idea is that you specify the list of the sites in sites.php and have several subfulders under /sites folder. At least it worked with Drupal 7. I'm sure there is no drastic charge with Drupal 8.
But be careful with cache. Mind which caches you want to keep shared or unique.