I speak multiple languages fluently and people are always surprised when I share that my vocabulary is seriously limited. I learned it is an advantage. I am forced to use simple words to explain.

On the opposite end: I had a coworker, I only ever got about 30% of what he said. I thought it's my Japanese skills. He used complicated sentences and words all over the place. But when I asked other Japanese coworkers, they told me they could not understand him either.