Try hard reset, it's easiest and fastest fix if it's software problem

To change WiFi password first you need to acess admin panel.To do so you need to go to special address when you're connected to WiFi router, usually 192.168.1.1 or tplinklogin.net, but that address...

Login address is usually 192.168.1.1 or tplinklogin.net but it can be also different.Check your router's back and see login address, then go there, login with credentials(usual admin as both name and...

You have two options:1)If you're still connected to WiFi but don't know password you can find password in your PC/Android(rooted)Do Google: "how to find WiFi password in Windows/Android"Or...

Router range depends on many factors. Make sure antennas are attached well, try changing antena angles and most importantly, don't put it in the corner.Try to place router in open area, with less or...