From my studies and research, I've found 3 Tools to use to test the speed of your web page.

Let's introduce you to each one.

1/ Google Developer Tools:https://developers.google.com/speed/pagespeed/

2/ GTMetrix PageSpeed Tool:https://gtmetrix.com/

3/ Varvy PageSpeed Tool:https://varvy.com/pagespeed/

What we need to do FIRST AND FOREMOST, is to BACKUP your WordPress Website and UPDATE PLUGINS

How To Backup Your WordPress Website?

1/ To Backup your Website, from your WP Dashboard, scroll down to Tools on the left menu, hover on the title Tools, then click on Export.

Since we want to Backup ALL your content to be safe, we'll leave it on the default - ticked on All Content. If it's not ticked, click on the radio button to the left of All Content.

2/ Now click on Download Export File and when the dialogue box opens, click on the Save button, then select the folder you want to save it in on your computer, then click on Save.

This will Save and Backup your WP Website to your computer, or as you have selected in your saving process.

Let's Update Your Websites Plugins Now

1/ From your WordPress Dashboard, scroll down to Plugins on the left menu, click on Plugins and check if any of the Installed Plugins need to be updated.

2/ Usually, there is a list of the plugins that need to be updated, so you could click on each one in the box to the left of it to Select it, then click on the Actions drop-down list at the top of the screen and then click on Update All.

This is a quick way to do all of them all at once instead of one at a time. If there aren't any, you're ready to continue!

Now that we have Backed Up The Website and Updated Plugins, let's Start The PageSpeed Tests On Your Website.