The "Poor" signal strength referenced in the first screenshot is the connection between your computer and the wireless router (looks like a mobile hotspot for you). Basically all you can do here is move your computer closer to the device "transmitting" the WiFi signal (the BlackBerry I guess).
You can't do much about the signal changing between 3G and 4G other than get in touch with your mobile provider. If your area doesn't get a strong 4G signal, then I'm afraid you're not going to have much luck. 3G can be pretty fast though, put your BlackBerry in direct line of sight to your PC WiFi antenna, around 2-4metres~ away, and that's where your optimum signal will be in that regard.