He told reporters on Boateng: "We are all happy with his development.
"We can support him as a coaching team, but it always depends on what he offers. In this regard, his development has been very positive.
"We will do everything possible to do the contract if he decides to stay here. He has had our support so far and will continue to do so in the future."
And on other players that have expiring deals he said: "These are also decisions that every player has to decide for themselves.
"They have undergone enormous developments over the past six months and were real top performers. The club also noticed that and I hope that it goes in the right direction."