I've problem with Wi-Fi on Lumia 520. For connect for Internet I must remove setting of Wi-Fi, again configure Wi-Fi, reboot phone for connect to Internet. Connect Internet sometimes takes shorter time, and sometimes takes longer time.
Other Wi-Fi devices work without problems. Just problem with my Lumia 520. How to reset the wifi router? I reset my password and use my passwor again, reboot my phone and it work, shorter or longer time.