Is it immoral to read scientific articles if you find them as pdf on Google without having access to some official libraries? I like to learn things even outside my university degree and I wonder if it is moral to read articles found online on blogs and other sources?
There's nothing morally wrong with reading blogs and most online sources, so I'm going to assume you mean published articles and books.

When it comes to journal articles and books, it depends. Many articles that are freely available online are legally published / published with the author's permission. Others are not. Obviously papers posted on the author's website, or websites like arXiv are okay, but for other listings it's a lot less clear. It's up to you to make your best judgement as to the legality and the morality of the access you have.

This also of course presumes that you think it's moral to support closed-access journals. Some people feel that closed-access journals are a bad thing and should be opposed. To those people, doing anything other than seeking out illicit versions would be morally wrong.