It's hard to add to the excellent prior post. Aside from narrowing your topic, you must realize that in order to fully understand and comprehend your subject, you must take the time to read and research it. Too many people today take the easy way out, reading condensed material on Wikipedia or Googling a topic and expecting all of the answers to be at your fingertip. I am a Civil War buff, and I have read dozens and dozens of books on the subject, but I still feel that I have only touched on a fraction of the info available. Plan to spend a lengthy amount of time reading, reading, and reading on your topic. It's the only way to fully understand it.
I am assuming that your question is about what to do when you have found a great deal of material in your research. Sometimes we feel like we are drowning in words. I have a few suggestions that I hope will help you.
First, try asking yourself if your topic is too broad. If you are writing a research paper, or even a thesis or dissertation, you will need to limit your scope of inquiry. Getting five million "hits" on a topic is a good clue that your search is too broad. Use the Boolean operator "AND" to narrow your search, in combination with a search term that will refine your results.
Second, rather than trying to read every article, work on reading the abstracts first. One of the purposes of an abstract is to help the researcher see if the results are at all relevant to the subject being researched. Only if the abstract is going to be of use to you should you read a full article.
Third, when you do find that you want to see a full article, there are some strategies you can use to make the process more efficient. The "Find" button will allow you to search for a word within the article, which will direct you to the sections that are relevant to your inquiry. If the entire article is likely to be of use to you, try reading the introduction, the topic sentences at the beginning of all the paragraphs, and the conclusion. Do not even try to read the entire article until you are done with the research phase.
Fourth, you need to accumulate all the articles that you will rely upon to write and then stop researching for a while. Those are the articles you will need to read, or at least read the sections that are germane to your topic. Many of us have a tendency to not want to stop the research phase, to keep on finding more and more interesting articles. It is important to limit yourself because no matter how many articles you read, there will always be some that you will not read. Sometimes, after you are done reading your "limited" pile of articles, there will be a new thread you will want to pursue, a new angle you had not considered before. And there is nothing wrong with that. Research should be a process of discovery. However, once again, you will need to stop yourself from going on forever.
Finally, there comes a point at which you must write. Keep your articles handy, in digital form, or in a pile next to you. Be sure that you do read the complete article or section you need before you write or as you are writing, since otherwise, you run the risk of using something in a way that is out of context.