Reading Comprehension

I am a non native speaker. I already got 600 score on TOEFL but can not get 50 percentile on verbal

I wonder my reading skill is weak or my vocabolary is weak

I do research and see that the GMAT passages dose not have new words which affect understanding. So, I conclude that my problem is not relevant to vocab but to reading skill

Is my conclusion correct?

Dose Any non native speaker have experience of this, Pls, give your idea, pls, help me

Hi Duongthang,
I am non native speaker, it seems the GMAT does not test your english ability, there are many words that even the native speakers don't understand, actually these words are there just to distract you, you should focus more on the structure and try to get the big picture.