By Dan Marsh Erling Haaland has only been at Manchester City for a little over 18 months, but his impact has been nothing short of seismic. The former Borussia Dortmund striker plundered an incredible 52 goals in 53 games in his first season at the Etihad, playing an integral role as City won the Champions League for the first time to complete a historic treble. The only downside for City is that there has already been plenty of speculation over when the Norwegian superstar will decide to embark on a fresh challenge. And comments made by the striker’s father, former City midfielder Alf-Inge, b…