The 23-year old German midfielder is a target for Manchester United as well as Spanish giants Barcelona and Real Madrid and with 18 months remaining on his contract, is hoping to soon make a call on what is best for his career.
"I have not made a final decision yet," he told BILD.
"BVB are the first team I am talking to, I will soon make a well-thought decision. But I am keeping my options open at this point.
"Borussia Dortmund have not set me an ultimatum.
"I am just trying to get healthy again and get back to my best form. That's the main priority for BVB and for myself."
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