Complex sentence: Being from the city, he is eager to take photos of the tree Marta and Colin warn him of the next door neighbors, the Marlings, who seem to be an angry, old couple who hate everyone.
Split into simpler sentences: Being from the city, he is eager to take photos of the trees. His aunt and uncle warn him of the next door neighbors, the Marlings, who seem to be an angry, old couple who hate everyone.