Responsive not working after converting html theme to Drupal theme
To create or convert a Drupal 7 responsive theme, it is not a good idea to start with stripping down and modifying a fully developed, non-responsive theme such as Bartik.

Instead you start out with a responsive starter theme or base theme framework, where the css is already reset for you and where the the framework is already prepared for you to add your own classes to construct whatever look and feel you're after.  Basically, you install your framework, then create a sub-theme, and use that you build your own responsive theme.

Good foundations for this is IMHO Zen, Omega or AdaptiveTheme (suggested by @Kojo in a comment), but many other alternatives exist.