Hi KH. I'm Greg, awarded MVP for eleven years, Volunteer Moderator, and Independent Advisor here to help you until this is resolved.
The Store apps are too new and undeveloped to trust for these functions which have always been settled by the internet web pages.
I'd use Speedtest.net from several browsers to find the average. You can use your choice of test as long as it's online and not some buggy app.
If you suspect you're not getting the speeds your paying for, you can optimize your router: http://www.maximumpc.com/article/features/ultim...
You can also try the steps here:
https://helpdeskgeek.com/windows-10/how-to-get-...
https://www.lifewire.com/troubleshooting-slow-i...
https://www.howtogeek.com/341538/why-is-my-inte...
I hope this helps. Based on what you report back I can answer any questions and may have other steps to perform.
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