Hey, @Carina! The site is looking good!
The issue you describe actually stems from rigid styling. You have used precise pixel values for width and height in desktop, tablet, mobile landscape, and mobile portrait modes. These values are getting inherited by your mobile portrait mode, causing the issues you're seeing. It's really best to deal with %s when working with width, considering devices in every class have different resolutions.
Here's a quick clip regarding some styling on your homepage:
And on the content page you featured above:
You'll note on the second clip, I inserted some quick pixel values for height as a temporary measure. You'll probably want to play around more with the styling!