Slow speed site

Hi,

I’ve just checked my website speed and it says my site is slower than 83% of the internet. (that can’t be good)

I have optomised all my photos and run a ‘purge cache’ plug-in on my site (https://www.srstrickson.com)

Is there an official way I can check the speed? And is there a way of speeding the site up? Or a way of checking what is slowing it down?

I’m sure this has been covered, but I’ve done a search and all I could see was a closed chat around 2 yrs ago.

Thanks for any help