How do I test my site speed?
You probably have tested your site speed various times geting different results. If you for example use Google PageSpeed Insights, you will get totally different results depending on if you have a 3G or a 5G network connection. In the city you might get pretty good results for your website, but when you make the test at the countryside, you get disappointing bad page speed results. If you use multiple tools such as Pingdom and GTMetrix you get a better understanding of your site performance and the factors that affect the speed. If you have not used speed test tools, you can first test the easiest tool - ThinkWithGoogle: https://www.thinkwithgoogle.com/feature/testmysite
What then kills your website speed? Typical mistakes might be caused by use of uncompressed images, slow insufficient servers, too many plug-ins that are connected to 3rd party services, old code and unnecessarily complicated website structures.