Make site responsive

I have made a lot of changes to the website since my last question. However I have one last thing that I have been struggling with. The theme seems to have very little/poor support for different screen sizes. Does anyone know of any plugins that could possibly be installed to allow me to quickly make the site responsive without having to hard code it in the CSS?

I have searched on YouTube for any plugins that can do this and I cannot seem to find any.

Thanks in advance

Courtney

via Chebli Mohamed