Summary: Your sitemap isn't split into many other sitemaps which causes all of the sitemap URL's to start loading in just 1 Sitemap which in turn causes a big strain on your server.
Description: It took more than 5 minutes just to load your sitemap. That is not normal.
Impact: Servers can lockup because of this. Look at this Github discussion about a similar issue to yours which has caused servers to lockup for another Webmaster experiencing the same issue as yours.
To reduce load, the sitemap can be split into many sitemaps.
This impacts your ability to run your web applications efficiently and will thus affect your ability to run your business smoothly.