Fairphone 3 with E/OS is getting hot while charging and has weak or no 4G signal after update

Thank you very much. At the moment the phones heat problem while charging returned back to normal.
I am left the 4G connection problem. It goes in and out of connect. On top corner of the screen it says 4G but only when it says 4G+ I do have connection.
Do you perhaps have a suggestions for that?