As you learn the Drupal API, you will often need to refer to the main documentation at https://api.drupal.org. This is the automatically generated Drupal documentation. It contains all the information about each function, class, method, where they are defined, where a brief description is used. Also on this site there is API help, I advise you to familiarize yourself with each of the sections:
If you develop sites on Drupal, then you will encounter each of the sections that are written there.
Also sometimes you just need to look at the sample and do the same. There is an examples module for this:
This is a set of modules with various functions that describes the basic things of the Drupal API.
In addition, use Google as a means to search for information. Sometimes solutions are quite easy to find if you make the request correctly. Google quickly provides the correct results on StackOverflow, Drupal Answers, and other similar sites. There are also many Drupal manual sites and articles that are also easy to find.
In order to find the right module, it is best to write:
To solve a problem, you can write
Drupal How to change/fix/find/resolve
Errors are also sometimes easy to find, for this you need to insert an error and remove all the paths to your files from it, and leave only the line and file name:
Fatal error: Class 'CommerceGuys\Intl\Country\CountryRepository' not found in /home/laptop/projects/project-name/docroot/modules/contrib/address/src/Repository/CountryRepository.php on line 14
You develop your own rules for finding the necessary information on the Drupal, keep track of which queries help find the information and which don’t. Using google greatly simplify and speed up problem solving and finding the right functionality. Thousands of other programmers use Drupal, and most likely another programmer already did your task before you, or your mistake already occurred to someone and you can find a solution in google.