Complex sentence: Flysch is typically deposited during an early stage of the orogenesis, when the orogen evolves the foreland basin will become shallower and molasse will be deposited on top of the flysch.
Split into simpler sentences: Flysch is typically deposited during an early stage of the orogenesis. When the orogen evolves the foreland basin becomes shallower and molasse is deposited on top of the flysch.