To measure the speed of your broadband you can use a free independent website, such as www.speedtest.net
Before testing, make sure the WiFi on your modem is turned off and that no internet use is in process (Such as Netflix or downloads). You will need to make sure the device you are testing is plugged directly into your modem via the ethernet cable.
If you are not getting the desired result, please change the server to ensure it is not an issue with the remote server.