Doesn't look like that Biga river. /rimshot
Incorrect. Greek rule was short lived, but Hellenization persisted until the 6th century AD. Persian rulers studied Greek (including Greek plays) and coins were minted in Greek even by the Sassanids until the middle of the third century AD. Persian nobles continued to send their youth to study in Athens until the Neoplatonic academy there was closed by the Procurator of Achaea in the 6th century.
He also confiscated the tuition paid by the Persian king for their study in Athens and the Romans had to cough it up after a Persian diplomatic protest.