Responsive formatting of pages.

Hi,
My page is mbwoodcraft.com and I have a very simple understanding of coding and websites. My theme is customizr.

I am currently struggling with the Wood Samples and Gallery pages of my website. I set them up so that they look good on my laptop, however when I look at it on my phone or on a smaller screen the pictures change position and no longer look evenly spaced out. Is there a way to fix this. I don’t want them to become static and not change at all, I just wish that if the screen changed they would follow a different set out.

Any help or advice would be super helpful. It’s a project I’m doing for my dad so I’m really quite out of my depth a lot of the time.

Thanks in advance.

Anita x