The 17-year-old has been in impressive form for the Germany under 17 side, having scored several goals in the European Championships and five in the World Cup.
His impressive displays have helped him break into the Hamburg first team and since doing so, he has notched two goals from three appearances.
Arp became his club's youngest ever goal scorer two weeks ago when he scored a consolation during their defeat against Hertha Berlin.
"I have a huge chance here and I'm really happy to be an integral part of the Bundesliga squad,' said Arp. "The hype is honestly a bit scary to me. At the moment, I just want to focus on football."