He was identified as a suspect in the 2007 disappearance of Madeleine McCann in 2007.
Bischof met him through a mutual friend and Brueckner told him he was "between jobs and had no money".
Brueckner moved into Bischof's home, near Hanover, shortly after Maddie disappeared.
"He was always anxious, never relaxed," Bischof told the Daily Mail.
"His eyes would always dart around the room when you were trying to have a conversation," he added.
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Bischof reportedly found that his tenant was selling drugs and stealing from hotels where he worked.
"I was uncomfortable and tried to encourage him on the right path," he said.
The landlord says he agreed to have the car registered in his name as a "favour".
He said he was surprised when police showed up to ask questions about the man and says authorities seemed "fixated" on the car.
He also told the Daily Mail the tenant would go on about his English girlfriend named Maria who he believed was in Portugal.
Brueckner is serving a sentence for the rape of a 72-year-old woman in Praia da Luz in the Algarve.
He also has previous convictions for child sex offences.