How to make friends with a store on Drupal?

Question

Drupal

How to make friends with a store on Drupal?
I need to fix the site on Drupal, but there is no one, so the random fell on me. But as soon as I went into the Drupal directory, I realized that everything is too complicated, so it's easier to ask knowledgeable people:

• How to edit layout?
  
• Where are the scripts/styles?
  
• Where can I find .php files for cart handlers and the like (working with the database, maybe modules)?
  
• What is the file structure in Drupal? Where is what?
  

Answer 1

Unfortunately, it is impossible to cover all your questions within a simple answer, the topic is too extensive, learning Drupal takes time. You should start by looking at the Drupal documentation https://www.drupal.org/documentation
Next, determine which modules are used and study the documentation for those modules.