In the past years Google has been putting more and more importance on responsive, mobilefriendly websites. Since so many users now browse from their mobiles and Google sets a high standard on good user experience, mobile friendliness has become an important ranking factor.
You can test the mobile-friendliness of all the web pages of your website using https://search.google.com/test/mobile-friendly.
It will give you a score and a detailed list of issues (and how to fix them).
