How to optimize loading speed my website

Slowness/high CPU usage could be due to (but not limited to):
– A poor or memory intensive theme. Switch to the WordPress default theme and test loading time and see if you see a difference. If you do, may be your theme can be re-written to be more efficient.
– Poor or memory intensive plugins. One by one disable plugins and test loading time and see if you see a difference. If you do, may be that plugin can be re-written to be more efficient.
– your server is slow (e.g., “process hang”, overload, you get a lot of visitors, other problems, etc.); generally, every inexpensive host out there is slow.
– I don’t know if you use CloudFlare or not but if you do I would suggest deactivating it and seeing if it helps. Also sometimes a good purge of the cache on CloudFlare can help.
– Lots of images can cause slowness. Also images loaded without compression.
– Lots of external content (facebook/ gravatar/ google adds, etc.) and redirects in general tends to slow sites down.

Useful codex:
– https://codex.www.ads-software.com/WordPress_Optimization

Thanks for your advice. I will try it. Thanks a lot

you are welcome ??

Same question from my side, just a bit more specific:
I tried to improve the loading speed for several pages (WP and non-WP) using Googles PageSpeed Tool Insights. Significant improvements I achieved by reducing Javascript, minimizing CSS and especially images.
One of the remaining suggestions is to optimize external images, like embedded twitter cards. But how should I take influence on that???