Maybe your device is not connecting to the correct WiFi hotspot, so it must go through a thick wall. If the interet speeds differ on your connected devices, however, the poor connectivity is likely either due to a local misconfiguration or device capabilities. If the internet speeds are the same for the weak and strong signal, it's likely an ISP issue. Just run multiple tests, one close to your WiFi Hotspot and one in the place where you're having issues because the signal strength diminishes. So to figure out if your connectivity issues are due to your ISP, your wireless connection or a local router issue running a WiFi Test will give you the insights you're looking for. Most of the devices on your home network today are not connected with a wired connection anymore. Running a WiFi Speed Test is the right solution for most people if they encounter connectivity issues as they are usually internet speed related.
