Celtic are now fully focused on preparing for the challenge of Borussia Dortmund in the UEFA Champions League. Having come through their weekend match with an electric 6-0 performance away to St Johnstone in the Scottish Premiership, the Bhoys know things are set to get a lot harder. Dortmund can’t be underestimated. They reached the final of the tournament last season and are financially on a different level to the Scottish champions. They have the quality to punish Brendan Rodgers’ side on Tuesday. Yet, it’s fair to say they have question marks surrounding them in the context of their own ai…