What router/modem or gateway do you have? If you have an Android phone, you can use a free app like WiFi Analyzer to check for interference from neighboring sites. If you are using the 2.4GHz band, try changing the channel to either 1, 6 or 11, choose the one least used. Other than that, you may have to replace your router with one with better WiFi range. If you have a gateway, I recommend replacing it with a stand-a-lone modem and a good router like the Netgear Nighthawk R7000. That unit has great WiFi range and uses beamforming technology.
It's important that your modem/router is as high off the floor as possible and in a very open area. I'd be happy to take a look at the modem/router and see how it's performing. Please send an email with your full address to: firstname.lastname@example.org.