Hey Ignacio,
The issue is most probably because of the menu buttons.
They’re minimum width in combination is 400px because of the there are 5 of them each with 80px min-width.
Please try hiding that container using the Hide During Breakpoints feature and check if the issue persists. If it’s fixed, display a Navigation Collapsed element to replace those buttons in mobile view.
If the issue persist, there could be other areas on your site that are non-responsive or having px based widths. In that case, I’d recommend that you duplicate your header, content and footer and load them up in a test page then remove elements one by one to narrow down and see what’s causing the issue.
Thanks.