Matías O. okay unfortunately the style guide that this was started on has nothing to do with Relume's style guide or components. It was one of the downsides to using the untitled UI style guide and components is that you will be forever limited by whatever components were originally released and this style guide. I think your best bet is to try to turn class sync off.
Essentially this Untitled UI style guide was a proof of concept collaboration with Jordan to show off the "My Library" feature when it was released - it was a free set of components but was limited in the number of components. With the webflow limitations, its not possible to cross-sync style guides in the way that you are looking to do here.
change preferences to use Relume Style Guide v1.5
You'll likely have to manually add your custom classes to sections to get them to match your site's design.