div out of body with bigger width

I'm fairly new to frontend so sorry if this is a rookie mistake. I want to create a div out of my body with bigger width (all available width) but don't know how.

I have a personal webpage at https://jiwidi.github.io/ where the body is centered with a fixed width. This works for me when having blog/text pages but I also want to add a photos section https://jiwidi.github.io/photos/ in which I would like to make the photos go out of this body and create a gallery with full screen width, something like this: https://www.w3schools.com/howto/tryit.asp?filename=tryhow_css_image_grid_responsive. Right now my pictures are limited to the body width and don't create the gallery look I want.

My problem is that I dont even know what modification to the style / html structure should I begin with. Is this a good practice? Any advice on how to approach this?

Thanks!