Changing the index page/gallery design just on mobile

Site URL: https://renerodlauer.com

Hey guys! I hope you are all doing good and having a great start in the week.

I just updated my website on the weekend and am very happy with how it looks on a PC or Mac, but, I really don't like two major things on my mobile version. I switched to the Avenue template and am happy with it but, even if I select "Thumbnails per row" to 1 - it will display two rows on mobile. Additionally the size of the thumbnails will get even smaller.

Is there any possibility to attack these two factors with custom css? I would love to make my mobile site index page with all the projects look as closely as on Mac/PC and it really is just the placement of the thumbnails and their size, so I hope there is a way.

Thank you very much! Attached you will find a screenshot of my website on Mac/pc and a screenshot of my website on mobile.

Best,
René