Dear Samsung Member,
Greetings from Samsung Customer Support!
Please be assured and to resolve "wi-fi" issue kindly follow the given below path and then try again:
1) Reset the device: -Kindly create data backup of your device via SMART switch mobile application or http://www.samsung.com/in/support/smartswitch pc suite.
Tap on Settings>Tap on General Management>Tap on Reset.
2) navigate to open the phone app>>tap more options(three verticals dots), and then tap settings>>tap on wi-fi calling>>tap the switch to turn the feature on.
Please be assured and to resolve "Overheating" issue please follow the below given steps:
1)Close background running apps.
2)Uninstall the unnecessary apps.
Overheating--Follow the link for more details :- https://www.samsung.com/in/support/mobile-devices/why-the-heating-issue-occurs-in-mobile-device/
If the issue still persist, kindly register your concern in Samsung Members app (Samsung Members app > Get help > Feedback > Error report).
Note: Please send device log files within 15 minutes of issue occurrence along with the exact issue details.
Thank you for writing to Samsung.
Samsung Customer Support