[ALL THEMES] My Website Is Slow. What Can I Do?
There are many reasons why a WordPress website is slow.
1. Use of too many plugins
The more plugins you use, the more resources your site needs. Thus, only use the ones that you need and trust. Disable all unused plugins to save the resources. Remember to update all plugins to latest versions.
To detect which plugins are poorly performing, use the P3(Plugin Performance Profiler) plugin
2. Use of too many large images
Modern websites use a lot of big images. Vistors love it. However, too many of them on a page can increase the loading time. In addition, if a theme has poor coding code, large images are used in the place of small ones. It means a full HD (1920x1080px) image is loaded instead of a 150x150px one.
Thus, make sure the page does not load too many images and images should be in the correct size. If you change theme, make sure you know this: https://cactusthemes.com/knowledgebase/themes-change-theme-now-site-slow/
3. Not cached
If you haven’t used a caching plugin, use it now. It greatly enhance the performance of your site. Two most popular caching plugins for WordPress are W3 Total Cache and Super Cache. Depends on your experience, choose the one you need. There is a detail post about this: http://www.wpbeginner.com/plugins/how-to-install-and-setup-w3-total-cache-for-beginners/
If possible, use a CDN to host images and media files (it is also mentioned in above article).
4. Not too powerful host
If you are using a shared host, bear in mind that it has limited resources. If you run a complex theme, such hosts may not handle well. Therefore, check your hosting capacity and increase it if possible.