If you've noticed that your wifi network doesn't seem to be running as well as it should, it might be time to reboot your wifi router.
Without getting into the nitty-gritty of how wifi works, the key is that there are really only three channels available that don't interfere with each other. Although newer devices support 5 GHz networks that don't suffer from this inherent problem, most devices still use 2.4 GHz which does (primarily because the range on 5 GHz is quite limited in comparison). So when you click on your Wifi menu icon to choose a network and you see fifteen networks, chances are almost all of them are trying to communicate on one of those three channels. As a result, signals get drowned out in the noise.
Most routers by default are set to pick the best channel (the one with the least interference) when they first start up. Rebooting your router can get you back on a channel with less interference, and as a result your range and speed will improve. To test and see whether it makes a difference, try running a speed test at fast.com prior to rebooting it, and then again when it's back online. Hopefully you'll notice an improvement.
If this doesn't work for you, and you feel like your speeds are much lower than what you're paying for, it's probably time to upgrade your wifi network equipment, or add additional access points to give a better signal over a greater area.