When is it permissible for a Muslim to pray 'Isha after Maghrib in Germany, where sunset is late?

The time for the 'Isha prayer begins with the disappearance of the twilight (shafaq), which is the red afterglow, according to the more preponderant opinion. Muslims in countries where the twilight disappears late must perform each prayer at its prescribed legal time. It is not permissible to combine the Maghrib and 'Isha prayers permanently due to the late disappearance of the twilight. Rather, combining prayers is permissible for other reasons, such as illness.