You’ll need to clear the WiFi setting cache as you have something getting in the way.
You might want to fully wipe the drive (format it) and upgrade to Catalina which is as high as Apple supported on your system.
Sadly, the world has press onward with newer HTML code and you’ll want to run OpenCore to jump to a newer MacOS so you can gain the better version of Safari or other web browser of your choosing as the older versions have issues.