How To Make My Webpage Responsive

I used THIS Webflow - Momentum
template to create my webpage.

I had no idea what I was doing so I sort of kept some stuff from the template and added my own. I got the laptop and desktop view to a point where I’m happy but even after watching many tutorials I can’t figure out how to fix the responsiveness for the other breakpoints.

Can someone point me in the right direction? I’m completely stumped.

Here is my site Read-Only: Webflow - SMMA Site)