Is there a way to display not all the posts in the blog, but posts from certain categories?
For instance, I have category-1, category-2, category-3, category-4 and category-5. I need the blog page to only display posts from category-1, category-2 and category-3.
Yes, just use the “Post Grid” element from Visual Composer. Select the categories you want to display in Post Grid Settings > Narrow data source.
Or just use any other blog element in VC. You have the option to display only one certain category from it.