One person he spoke regularly with was Anis Amri.
The duo spent their time travelling between radical mosques in the west of the country to flats of ISIS supporters in Berlin.
Bilal A. is now being held for fiddling euros worth £2,000 from asylum authorities in three different places in Germany. But media reports say that he is expected to be hit with terrorism charges in the coming days.
He was sentenced under one of the many aliases he used #8211; Egyptian-born Abu Bakir, even though he came from the Tunisian town of Bizerta.