Please take a look at the flowchart below to understand how to update Magento 2 Extension.
1. Does the extension core files were modified?
If your website was developed in a proper way, then the answer is "No", and it is good for you. If you not sure then you can use code merge tools like "Meld" to compare code from the original archive and your website.
2. What is PHP Composer?
It's the package manager for the PHP, it allows you to manage dependencies of Magento2 extensions and PHP libraries. It also facilitates the upgrade process.
3. Does the Composer package exist for the extension?
If you use Magefan extension, then answer is YES. You can install and update any Magefan extension via Composer. Please contact extension vendor to find out if their extension can be installed/updated via the Composer.
4. What to do if I get error "Module 'Company_Module' from 'app/code/Company/Module' has been already defined in 'vendor/company/module'." ?
Please check this article.
Do you have more questions? Please let us know in the comments below.