Helga Mykytej

I have been working with Magento for 5 years, so I can only advise you one thing: if your business is going to grow and grow bigger then you made the right choice with Magento 2, if not then go to another platform, that is cheaper.
So choose the best option for you!

Our website needs to be improved in the SEO branch, so any recommendation on how to do that, exactly what to read to know what to do at first?

As for me, SSO offers a lot of functions: it increased security, productivity gains, and fewer IT help desk password resets.Thanks to SSO, I can log in only ONCE.
Yes, it's not the best security measure in the Internet, but if your intent is to strengthen security, improve productivity, tighten B2B collaboration and drive down help desk costs at the corporate level, SSO is a timely and effective solution to a sizable issue.

Static nested classes are not really inner classes; their sole purpose is to serve structuring and scoping mechanism for logically related types.

Read as much as you can on the uses, advantages, and downsides of both methods and make the right choice.
And I agree with your method,stick to black-box testing and test only public methods.Whenever a public behavior is checked, the private implementation is also implicitly tested and your tests will break only if there is a certain problem.

If you want to master Java properly, you should probably go through all stages of the official Java tutorial, available free of charge here:

The Java™ Tutorials

Best Java Online Courses:

The Complete Java Developer Course;

Object Oriented Programming in Java.

Therefore, once you have mastered the basics, I would recommend subscribing to the official Java magazine, which outlines all important changes in the language itself and the auxiliary technologies that enable to run Java code:

Java Magazine

There are many factors and perceptions that matter a lot when we compare any languages, frameworks, or tools. We know that Kotlin is based on Java and you can’t actually compare both these languages due to an influence of one on the other. Many have adopted Kotlin and are enjoying tangible benefits of it, and there are developers who are stuck with Java in android app development. One thing is certain that Kotlin has potential to replace Java language but it may take more time than we imagine.

Kotlin offers many advanced programming features than Java.

Take a look at the comparison of features (developers’ perspective):

I am talking about Magento and Shopify and some other platform for ecommerce website.This is one of the problems, that every online store owner faces. This is very important and life changing choice, so I need to go along all the pros and cons of all platforms in order to come up with the best option for the business.

Since it's a method, to call it you should use parens afterwards, so your code would then become:

if(isValid()) {
   // something
} else {
   //something else
}

Whick framework do you prefer to use for e-commerce? Please write all pros and cons