[Closed] Site very slow when WPML activated

Background of the issue:
I am trying to get the site loading normally, but it is very slow when WPML is activated. The issue can be seen on this page: hidden link

Symptoms:
The site is very slow when WPML is activated. Some pages never open.
I sometimes get this error :

Service Unavailable
The server is temporarily unable to service your request due to maintenance downtime or capacity problems. Please try again later.

Additionally, a 503 Service Unavailable error was encountered while trying to use an ErrorDocument to handle the request.

Questions:
Why is the site very slow when WPML is activated?
How can I get the site to load normally with WPML activated?