However, he insists that they will not spend their funds lavishly and will limit the spree to their budget.
"We will continue to not spend more than we have earned," he told German TV football show Doppelpass.
"We are not depended on a transfer fee [for striker Robert Lewandowski]. My wishful thinking: Robert is still with us next season.
"So far, nobody has contacted us. If a club approaches us now and offers what we believe is a lot of money, we will consider it."
Lewandowski has been linked with a move to Bayern Munich in the summer.