This Error means, that your Webserver takes too long to send a response. As you can see below, it takes 7 seconds until the first bytes are sent, which is way too long. (This should not take longer than a second or two)
time_namelookup: 4,542
time_connect: 4,837
time_appconnect: 0,000
time_pretransfer: 4,837
time_redirect: 0,000
time_starttransfer: 7,413
----------
time_total: 8,955
It seem like you are using Wordpress, this is a common issue with it. You might want to look into using a caching plugin or proxy, like Varnish / nginx to improve load time.
