Website Slowness,Email Question,Error

Good Morning

my website is http://www.jdgamingit.co.za

I have a a few questions

How do i increase the speed when editing within the wordpress admin section off my site as currently when i do this it takes a extremely long time, i have tried the disable all plugins and it has helped a little i removed most plugins and now only have the essentials

How do i resolve the following error
WP HTTP Error: 0: php_network_getaddresses: getaddrinfo failed: Name or service not known, this error when googled leads me to many variants of the error i experienced the error when trying to activate jetpack i have since deleted the plugin but i still see the error on my dashboard

Also can someone please explain to me the process or steps to configure email notifications within the site, this is for WooCommerce to send notification emails. I am aware that WP is not a mail capable and that certain items must be changed within PHP i just need a more simplified explanation if possible.

thank you