Installed and activated child theme, looks wrong.

Hi, I have installed and activated the theme by using the child theme both were uploaded.

I’ve flushed cloudflare cache, but the website does not look look quite right when comparing with the Demo page. I would expect some differences due to content yes.

Some issues I’ve noticed so far:

1) The footer does not stay at the bottom of the page, there is a large white gap.
2) Menus take a short time to load, but creep down the page whilst it is loading.
3) Pages appear to be missing background? Font hard to read etc.

How can I correct these issues and make it look good?

Thanks very much.