Hello! I am by no means a webflow expert, but I'll try to help out!
I just checked out your video page and tweaked a few things.
Your body element "more-videos" is stuck at 1260 width. Idk why that is, but I renamed this to reset the class. You can rename to anything that doesn't already exist on that site.
Your element "dynamic list wrapper" is set to 1260 width. Change this to auto and place 1260 on the Max width. This is the reason why the page is bigger than the screen size when sizing the browser. (I also changed this to auto before I had to rename the body element, and the body element was still stuck at 1260, so again, Idk why the body element is stuck at 1260 with that class name)
Your element "dyn flex video" is set to 400 width. This is why the items are staying the same width instead of sizing with screen. Change this to 33.333% on desktop, 50% on tablet, and 100% on mobile(on mobile, also adjust the height to auto and maybe take the bottom margin down to 50px or so).
Everything seems to be working ok for me when I did this. I hope this helps sir!