Goalkeeper Diant Ramaj was transferred to the Dortmund team a few days ago, and was immediately loaned to the big Danish team, Copenhagen, until the end of the current season.
But Ramaj's debut at Copenhagen didn't go as he had hoped.
Copenhagen suffered a 2-1 home defeat to German Bundesliga side Heidenheim.
The hosts created a one-goal lead in the first minute of added time of the first half, when striker Jordan Larsson scored.
But the team, which is fighting for survival in the German top flight, responded with two goals in the second half for a 2:1 victory.
It was the first match of the Conference League knockout playoff stage.
Thomas Keller in the 59th minute and Tim Siersleben five minutes before the end, scored against the 23-year-old Ramaj.
