BVB have been linked with players such as Kevin De Bruyne, Christian Eriksen and Henrik Mkhitaryan in recent months as they search for a replacement for Mario Gotze, but have so far been unable to add a creative midfielder to their squad.
|20/1||Borussia Dortmund are 20/1 with Paddy Power to win the Champions League
"We are still very ambitious. That means that we have €50m to spend on new players - including Sokratis [Papastathopoulos]," he told Bild.
"Money can solve things pretty quickly in talks with other clubs. However, we do not only have to be ambitious from a sporting point of view, but have to make intelligent decisions financially, too.
"That's why things are taking a bit longer this summer.
"We will sign two or three attacking players and one of them will be a player for the future. I won't mention any names, though. People shouldn't let rumours on the Internet drive them crazy."
Dortmund have so far only signed defender Sokratis from Werder Bremen for of a fee of around £8 million.