The 31-year-old helped Dortmund reach the Champions League final last season as well as representing Germany at this summer's Euros and has been an impressive talent since breaking through with Hannover 96 and Werder Bremen.
In his first interview the striker states that his goalscoring will not stop at the Hammers and he cannot wait to get on the pitch with his new teammates.
“I am very happy to be here, also a little bit excited,” he beamed, speaking to West Ham TV. “I can’t wait to get on the pitch with my new mates.”
“I think there is a lot of quality here, and for me, it is important to have the guys behind me. It’s a dream because you have (Lucas) Paquetá, (Jarrod) Bowen, (Mohammed) Kudus, and now (Crysencio) Summerville as well.”
“There are a lot of very good players who can assist me, and if I get assists then I can score. I believe I can fit into this team very well.”
“I think we’ve got a lot of fighting players in midfield and defence as well, and I like the feeling when I know I can go to war with them.”
The German feels the weight of the West Ham shirt and feels he can find success at the club as they challenge for European football.
“In Germany, I just played for big and traditional clubs. It was always important for me to have the feeling that the shirt had a bit of weight to it, and I think West Ham are also another big and traditional Club,” he explained.
“I know Tim Steidten very well because we have history at Werder Bremen together, and I had a very nice feeling. I spoke with the Head Coach, I watched some games and I know some players, so from seeing this I can see that there is a lot of quality in the team, a lot more than ninth place, and hopefully we can do better next season and reach the European places in the table.”
“The fans want to see a successful team, see a team that gives everything on the pitch, and I hope they will be happy with me as I always give my best.”
Hammers boss Julen Lopetegui was a huge factor in the move as the striker explained his role in making the decision.
“The manager was a big reason for me making the transfer to West Ham,” he said. “I have been thinking about West Ham for a long time now, know the Club now, and have watched some of the games from last season.
“Lopetegui was important for me; his play style is important for me, and I need this to bring my best performance on the pitch. He knows that and will try to give me this.
“We have so much quality in this team, and when you see the players in the starting XI, they are of such great quality. If we work hard, be brave, and be patient, then we will have a very, very nice season and can surprise some other teams.”