The Fulham boss has been impressed with the young German right-back since he joined the Cottagers and wants the player to stay with the club.
"He's done very well. He's still young and he's learning but he's been very impressive and we are looking to do something permanent with Arsenal," he said.
"We are in negotiations but we'll have to wait and see.
"I think they are being a bit cautious because of their suspensions. At the end of the day it's up to Arsenal whether they want to sell him or not."