I found it very difficult to make myself understood.

Literal

Understood-receive [nominalizer-の] [subject-が] considerably difficult [quotative-と] thought.

理解してもらう (to be understood / to get someone to understand) uses てもらう for receiving the benefit of being understood. ずいぶん難しい (considerably difficult) uses ずいぶん for degree. The challenge of communication across a language or cultural barrier.