Google Fonts don't change


I am “creating” the front page and I wanted to change the fonts, so I watched the video in the documantation and did as it suggested. But the fonts do not change.
I want to use Lobster for heardings and Roboto Slab for the text. And I need Latin and Cyrillic. What can be a problem?
I also wonder about the color of the headings. How do we change it?