#!/bin/bash

sed '
  :a
  $! {
    N
    ba
  }
s/=\r*\n//g
s/\(=E4\|=C3=A4\)/ä/g
s/\(=F6\|=C3=B6\)/ö/g
s/\(=FC\|=C3=BC\)/ü/g
s/\(=DF\|=C3=9F\)/ß/g
s/=20/ /g
s/=3D/=/g
'