Complex sentence: Rosenqvist opened up a two-second lead over di Grassi (who had battery temperature issues) and the second Mahindra of Heidfeld had closed up to the Brazilian driver who was forced to use FanBoost to defend second place.
Split into simpler sentences: Rosenqvist opened up a two-second lead over di Grassi (who had battery temperature issues). The second Mahindra of Heidfeld had closed up to di Grassi who responded by using FanBoost to defend second place.