Biereth, who was born and raised in London, is a regular with Denmark U21s - who he qualifies through his father.
For a record fee of &euro5m, Biereth was signed permanently by Sturm Graz.
"Success at Arsenal is not the beginning and end of a career. There are many ways to have a successful career outside Arsenal," said the 21-year-old in the interview.
The feeling of "belonging" in Graz was a decisive factor in the move.
"I felt there was unfinished business after we won the double last season. Both in the atmosphere itself and in relation to the coach, the sporting director and the players. I felt like I was part of something. And the opportunity to be the first striker for a Champions League club at the age of 21 was irresistible," said Biereth.
The former Arsenal player recently met Donyell Malen, scorer of the goal in Dortmund's victory over Sturm Graz last week in the Champions League, who has enjoyed great success at PSV and Dortmund since leaving Arsenal, where he never had the chance.
"There are many examples like this, not just from Arsenal but from other academies too, where you leave very young if people think you're not ready for the first team, and you gain experience elsewhere. Then, a few years later, we showed that we were probably ready," said Biereth.