Upfront Builder - Panino Theme not functioning

Good morning all !

I'm having some trouble using upfront with the Panino theme:

After installing Upfront for the fitst time, it wouldn't go behind the 'loading screen'. I uninstalled it then, uninstalled the themes, and reinstalled Upfront. From then it works.

But now the Panino theme seems to be corrupt: although it is loading, the navbar for example doesn't stick to the top of the page, some css is missing, ...

My question is: how do I completely remove the Panino theme and reinstall it 'out of the box'?

I already reinstalled it but then it seems to get it out of the cache or something: I only changed the text in the yellow circle, and even after a full 'remove' and reinstall, the text is still changed and the theme is still corrupt.

Thanks all for your help !!