Why is the reception speed less than the upload speed by 2 times over Wi-Fi?

Question

WiFi

Good afternoon, colleagues.
Router - tp link archer c20 . Frequency - 5Ghz , ac standard . Interfaces 10/100.
The speed declared by the provider is up to 100Mb.
All measurements were taken on speedtest. (I know that this is not an indicator, but the torrent gives approximately the same numbers + -)
With a cable connected, through a router, on any server it shows: ~ download - 100, upload 100.
If I check on the phone, via wi fi, the same speedtest, then all but one server show the speed: ~ download - 50, upload 100.
And one of the servers shows the speed via wi-fi: ~ download - 100, upload 100.
Before that, there was another provider, it showed wi fi speed: ~ download - 100, upload 100. But I made a mistake that I was testing on an automatic server and did not pay attention to which one. And probably all the tests that I did. were made on this single server which still shows 100/100.
+ cable, providers shared my patch cord on different cores. But I think this is not relevant, since the speed on the computer is 100/100. And now, another provider's cable was cut out.
And it would be all the same to these numbers, it works and figs with it, but a smart set-top box is used to watch TV. (patch cord to connect the set-top box, there is no way, it does not have a connector. Only WiFi) And streaming video occasionally slows down. (YouTube and other platforms work without problems) It would be possible to attribute all problems to this service. But with a friend, there are no such problems. He has the same provider as I have at the moment. But the speed is up to 1GB. And because of this, I conclude that all the same, the service lacks WiFi speed.
Who will advise what? This is the first time I've come across something like this :) And are there any solutions at all?) Or at least what you can try)

Answer 1

And one of the servers shows the speed via wi-fi: ~ download - 100, upload 100.

How many times were measurements taken? you need five times (at least 3) for the average statistical.

When the cable is connected, through a router, on any server it shows: ~ download - 100, upload 100.
If I check on the phone, via wi fi, the same speedtest, then all but one server show the speed: ~ download - 50, upload 100.

There is such a thing, the utilization of the WiFi channel on which the router operates depends on who else is on the same channel, this does not mean that the consumer must be connected to your router, the channel utilization is affected by the number of wifi devices on the air of this channel. You can download the wifi analyzer utility to your phone to see how many other devices are on your channel. After that, in the settings of the router, you can often change the channel. If the mode is set to auto , then the TP Link routers , the download is checked when the router is turned on, and it remains there no matter how many more devices appear later. Therefore, you can check it again by turning off the router, measuring the speed and restarting it again.