Generally speaking, old and outdated software is a recipe for trouble. Specifically, WPML plugin has gotten much faster since version 4.2.8. You could see load reduction of up to 60% when moving from old WPML versions to current ones.
Caching plugins prevent your server from doing the exact same work over and over again. At the bare minimum, every WordPress website should use page caching. Beyond the obvious page caching, different plugins offer object caching, mem cache and other server-side optimizations.
The “host” is the computer that runs your website. You know that some computers are faster than others. Running on a fast host will directly make your site faster. WPML recommends a list of great hosting companies that specialize in WordPress.
There is no reason for WPML to cause your site to be slow. If you are feeling performance issues and need our help, please open a support ticket. If there are any performance problems due to WPML and we cannot handle them fully, we will refund your order. We can refund orders up to 12 months from the purchase date.