Borussia Dortmund have signed German youth international Jeremy Toljan on a five-year deal from Hoffenheim as they look to strengthen their backline, the Bundesliga club said on Wednesday.The 23-year-old, a recent under-21 European champion who also won a silver medal with Germany at the 2016 Olympic Games, made his league debut at Hoffenheim in 2013.”Jeremy can slot in on both the left and right of defence,” Dortmund sports director Michael Zorc said in a statement.”He was one of the cornerstones of the side that secured the title forGermany at the U21 European Championship this summer. He is a playerwith great potential.”??? #Toljan2022 pic.twitter.com/ym3YXZ36su- Borussia Dortmund (@BVB) August 30, 2017??? This is how we do it. #Toljan2022 pic.twitter.com/LDAkdDx8gE- Borussia Dortmund (@BVB) August 30, 2017?? Contract extension and loan for Felix #Passlack: https://t.co/rUPh0Fz1x3 pic.twitter.com/mWGQnuuey0- Borussia Dortmund (@BVB) August 30, 2017Dortmund, who will compete in the Champions League this season, also extended the contract of 19-year-old defender Felix Passlack until 2021 but have sent him out on a two-year loan deal at Hoffenheim to gain more match practice.