Are you using web-forms or MVC? You can check the Feather
module in Sitefinity and the build-in Frontend packages available
, which provide responsive functionality.
If not the case, can you please provide more information about the steps performed. If you prefer you provide some custom resources here or to open a support ticket.
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Sitefinity CMS Ideas&Feedback Portal
and vote to affect the priority of the items