Site not scrolling and scaling properly

I’m having issues with my site: https://www.jacques.tv

On certain web browsers (FF), the site is being cut off if the browser window is not large enough. And my scroll bar doesn’t seem to allow access to the rest of the content. You have to resize the browser in order to see all of the content.

Any ideas? It’s a modified WP site. Apologies if this is covered somewhere else. I’m pretty new to WP.

Thanks in advance.

Eric