Is it permissible to pray Maghrib before its time to avoid missing its time and the entry of the 'Isha' time?

The entry of the time is a condition for the validity of prayer, so prayer performed before its time is not sufficient. If you work in one town and reside in another, and the distance between them reaches the distance for qasr (shortening prayers) (83 km), then it is permissible for you to delay the Maghrib prayer and combine it with the Isha prayer upon arrival. However, if the distance is less than the distance for qasr or if the journey is within the city, the ruling of travel does not apply to you, and the prayer must be performed at its prescribed time. If it is difficult to disembark, you may pray inside the car according to your ability, and it is preferable to repeat it after arrival as a precaution. Some scholars permit combining prayers out of necessity, provided it is not taken as a regular habit.