Henrikh Mkhitaryan, Sokratis Papastathopoulos and Pierre-Emerick Aubameyang have all signed for the German side this summer, as Jurgen Klopp's team look to compete with Bayern Munich for the Bundesliga next season.
"I think that during the training we saw that the new guys have great qualities," Schmelzer told reporters. "If you look at Micky (Mkhitaryan) during training, he has some incredible movements, also Sokratis in the back is acting as if he'd been here for a few years already, and also Oba (Aubameyang] has great qualities.
"The new purchases are spot on, and like I've said, we are trying to integrate them into the team as well as we can, of course there are difficulties with the languages, but we have an interpreter and will manage somehow.
"Then at the beginning of the season the three will have adapted to our philosophy so that we can start the season successfully."
Schmelzer has spent his entire professional career at Dortmund.