Thanks for providing a ‘Read-Only’ link.
As Jean mentioned there are further column settings that will enable you to adjust their layout based on different breakpoints. Have a look at the image below to see how to access those settings. (looks like you’ve already discovered them).
The columns will stack as per the various viewport widths (as per mobile/tablet screen size) when you change the browser size.
As a side point - use of columns is kinda the ‘old way’ we used to do things. A much more powerful and flexible method is to use Flexbox or Grid (responsive by default), however, there is a bit of a learning curve to get to grips with fully using it.
Also, I note that you are using specific pixel settings on some elements, just be mindful that when designing responsively, use of specific pixel dimensions can result in unexpected results, generally we try to use responsive units like %ages, VW/VH, rems/ems etc (A whole lot of terminology, basically meaning responsive)
Can I ask are you trying to add pages to your existing website?, change your website to Webflow platform? or just learning?