@mariaszajer, The site description is typically used for a short statement telling what the blog is about. The following would get you what you want I think. Basically you keep the first paragraph in the site description and then you add the second paragraph using CSS. The second paragraph would be added between the quote marks in the following where it says TEXT_HERE. You would then remove the second paragraph of text from your site description at Settings > General.
You would add the following to the custom CSS at Appearance > Customize > CSS. Delete the informational text.
If you want more than two paragraphs, it gets more complex, but could be done.