What is the correct way to learn Magento?

I want to learn to use Magento, not for developing modules, only for building a simple ecommerce site.

Magento seems to be very complicated, always will encounter various errors.

Also, always need to use Composer.

But I don’t want complicated functionality.

What is the correct way to learn Magento? I only want to build a simple ecommerce site and can speed up its site speed.

Thanks!