Have you an android mobile phone?
If so get WIFI Analyzer by Farproc
https://play.google.com/store/apps/details?id=com.farproc.wifi.analyzer
Install this free app on your phone and check your wifi channels use, have a look see if the strongest signals of your neighbours is on the same channel as you, if so figure out how to enter your router admin pages and move the channel to the nearest empty one.
You will probably find that the wifi works a lot better then.
Also:
Is the wifi router perhaps sat next to the fridge/freezer - behind the TV etc?
If it's in a sheltered location then the signal will likly be blocked to you - temporarily move it and see if the signal improves (this can be someone holding it in an unblocked position while you run some tests).