If your phone is having WiFi and bluetooth problems, the two most common utilities for addressing this are the system updates and network settings.
First go into Settings > System > System Updates and make sure the phone’s software is up-to-date.
Then, go to Settings > Network & Internet > Airplane Mode to turn Airplane Mode on and then off again.
If this doesn’t work, perform a network settings reset in Setings > System > Reset > Network settings reset.
Finally, is all else fails, a factory data reset may be the only option.