What is the final time for performing Maghrib prayer, whether as a make-up or on time, and is it permissible to delay it to avoid missing congregational Isha prayer?

The time for Maghrib prayer begins at sunset and extends until the horizon and the red twilight disappear. The entry of the 'Isha prayer time ends the Maghrib time. The best time to perform the Maghrib prayer is at the beginning of its time. It is not permissible to delay it until after the 'Isha prayer time has entered, except with a legitimate excuse. Whoever catches one unit (rak'ah) of the Maghrib prayer before the 'Isha prayer time enters has performed it on time.