Please go to this website.
There is a lot of advertising on this website, so please refer to the following screenshots to find the right button to click and information to send us:
The page will load a screen with your Internet Service Provider (ISP) details with a yellow "GO" button to start the test (see screenshot below). Please click this button to start to test.
During testing, you will see the speedometer moving as can also be seen in the screenshow below.
When the test is done, you will see your ping, download and upload speed in the top of the window (as displayed in the screenshot below). Please send us these numbers.
Note: The IP-address details in the screenshot below are blurred for privacy reasons, but this information is not important for determining your internet speed.