Translation of wesentlich

In the meantime I am listening to some Spanish CDs. They are intended for the car, but no one can tell you when to listen to it, how many times and how often. Please understand that I work a lot.
Did you hear about the earthquake this morning in Greece. This is really terrible, I think that quite a few viligars lost their lifes and many more lost their homes. I am really sad for all of them.
I went to the desk of Aerolineas Mexicanas and postponed my flight by two days. I did not have to get prepared as I had done some homework before coming here. The backup plan was Isla Mujeres.