I can do this project. I've built a lot of responsive sites. You can see some work at [login to view URL] and most recently [login to view URL], I am an expert with CSS, I'm looking to build a solid reputation on Freelancer so I am putting 110% effort into all the jobs that I am awarded. You can see the ones I've taken so far have excellent reviews.
I would be more than happy to create an extra stylesheet that would include a couple extra breakpoints to your site to make it look better on tablets and small phones.