Complex sentence: Habima has been officially considered the national theatre of Israel since at least 1958, the year in which it received the Israel Prize for theatre, such year being also the first year in which the Prize was awarded to an organization.
Split into simpler sentences: Habima has been officially considered the national theatre of Israel since at least 1958, the year in which it received the Israel Prize for theatre. This was the first year in which the Prize was awarded to an organization.