Why is my car overheating so fast. on 1999 Audi A6 Quattro

my car overheats after 10 minutes whether idling or driving.
this all started after a flood 2 months ago, overheated once then and then; first drive after car finally restarted. last week it started overheating every time I try to drive it.
engine light come on and codes read (1)bad catalytic converter bank 2 below threshold and (2) cylinder 1 misfire

Asked by for the 1999 Audi A6 Quattro