The talented youngster joined City from Ajax back in 2014, and has only made 12 appearances in the U23 team so far this season.
Reportedly, Guardiola's side did extend a new contract offer to the winger, but Dilrosun rejected the offer based on the terms.
The 19-year-old travelled to the German capital at the weekend in order to smooth over the terms with Hertha, before completing a medical and signing the contract.
City will be able to claim a compensation fee of approximately £200,000, but miss out on the £1million pay-out they could have received if Dilrosun had opted for a rival Premier League side.
Standout matches today