Brighton officially announced that the team signed Dortmund midfielder Kadera.
Caldera has previously followed Manchester United for trial training, after agreeing to join, he will first join Brighton's U23 youth team.
Kadra, who is only 19 years old this year, has German and Lebanese nationalities. He joined the Dortmund youth academy in 2016.
Caldera has not played for the Dortmund first team. He can play central midfielder, full-back, midfielder and winger. He played 18 times for the Dortmund U19 youth team in the league last season, scoring 1 goal and sending 5 times. In addition, he also played 6 times in the Youth Champions League, scoring 1 goal and assisting 2 times.