Hi there,
your home page is built using Visual Composer and for some reason it looks like it is requesting every single featured image you have on your site – around 700 in total. So the page is taken a huge amount of time to load.
If you visit a single post or an archive page, which is GP, then you will see it loading in a more respectable time. To improve their speed i would look at reducing the number of related posts on your single post and the number of posts displayed on the archives.