Forget about WiFi for a minute...
What is your speed when you connect your PC to your router with a CAT 5E or CAT 6 ethernet cable?
There are many "speed test" websites and downloadable programs, but this one seems very trustworthy.
https://www.speedtest.net/
Your ethernet speed should be about 90% of the speed you are paying for. Remember, the WiFi "speed" will ALWAYS be considerably lower than when you are directly connected with an ethernet cable. And the WiFi speed will get exponentially slower the further you move away from your router.
Also, when choosing which radio frequency (WiFi signal) to use, the 2.4 GHz frequency can travel much further than the 5 GHz frequency, BUT the 2.4 GHz signal speed is slower and the 5 GHz signal speed is faster. So if you have the choice, go with the 5 GHz signal.
Test it for yourself and tell us what you get...