Why do translators find Kafka's The Metamorphosis difficult to translate?

Nowadays it is difficult to find an original copy of KafKa's novella which I am referring to is The Metamorphosis. Mostly, available copies now are the translated copies.

At first, the translators find difficulty in translating the Kafka's The Metamorphosis because the words being used in the novella are very confusing, it has a lot of meaning.