Hey Ashley,
The hamburger and the slow image issues are separate from the scrolling issue and it’s strongly recommended not to mix topics in a thread as it often leads to confusion and further back and forth. I’ll just comment on them but if you have further questions, please open a separate thread for different topics.
Regarding the hamburger, the page needs to completely load before you can click on any Javascript-powered feature like menus. What’s taking the page to load slowly could be the slider (Slider Revolution). Try opening a different page without the slider and see if the hamburger will open the Off-Canvas quickly.
Regarding the image, this is not a theme issue. You will need to improve your overall website performance. We have an article about it but since the scope of the topic is beyond the functionality of the theme, we cannot provide further guidance. See https://theme.co/docs/how-to-improve-site-performance
Hope that helps.