Parallax horizontal gallery

I’m putting together my portfolio and struggling back and forth with responsiveness. A big issue has been a feature I’ve used in one of my case studies. It’s 3 rows and div boxes with 5 images in each, with a slight offset so that they opposite to each other as you scroll down. The overflow is really bad though, especially on mobile and I’m having trouble sizing it down.

My screen on landscape in particular keeps getting cut off and I can’t figure it out, I’m skimming through tutorials left, right and centre.

Any ideas? Or has anyone seen something similar that I can use as reference?

Here is my public share link: LINK
(how to access public share link)