Reboot when uninstaling the application LG G4
Have you installed any custom software on your phone recently? If so than that could explain some issues. First of all the bugs you are experiencing with the settings, but also when trying to update the phone. Many of the custom versions of Android do not support the OTA (Over the Air) updates. 

However, if you do have stock version of Android there could be numerous issues. My recommendation would be to backup all of your files and simply restore your phone. Sometimes this can resolve any internal issue that Android is experiencing.

Hope this helps.