Striker Serhou Guirassy is poised to make his Borussia Dortmund debut in Friday’s Bundesliga clash at home to Heidenheim. The close-season signing from VfB Stuttgart has yet to play this term after a knee injury. “He is making an excellent impression in training. He’s training without the handbrake. He’s fully involved,” Sahin told reporters on Wednesday. “We’ll have to see whether he makes the starting XI or the bench. We still have two more sessions.” Forward Giovanni Reyna, on the other hand, will be out for several weeks due to a muscle injury sustained on international duty with the US. G…