Hi,
Hope you have resolved your slow internet issue completely, just joined and see that information given was lacking regarding 50mb max over Wi-Fi from your original comment. If you are using 5ghz band, then the device you are using probably only supports the 802.11a band, which supports a maximum of 54mbps.
To support up to 600mbps on either 2.4ghz or 5ghz channel, you would need a device which supports 802.11n, or to support up to 1.3gbps over Wi-Fi you would need 802.11ac networking device running on the 5ghz channel. Your router may support all modes, but the network device in your phone/phablet/tablet/laptop could be the limiting factor as they maybe using older tech which doesn't support newer faster transfer rates. Hope this makes sense regarding the hardware.
Distance and network congestion also plays its role in slowing speeds down.