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Have you tried getting a fresh copy of the iFrame embed code and re-embed it on your website?
Even on just a desktop browser, the part of your content is already cut off. Here's a screenshot of it:
You can see that the <main> element only have a height of 500px and it doesn't cover everything.
The form embed code that you have also uses a height of 100% which will not work because the height property only accepts "px" or "em" in the iFrame.
I suggest that you check with your developer on how to fix the layout. I also suggest getting a fresh copy of the iFrame embed code, there's a script included there that should make the form more mobile responsive. The height property of the frame should also be in "px" or "em", not "%".
To learn more about the iFrame embed code, you can check this guide: https://www.jotform.com/help/148-Getting-the-form-iFrame-code
I hope that helps.