Welcome to PrepAdviser and thank you for your question.
The GMAT is not a language test. It tests your analytical skills and quantitative skills in English. So, the first thing you need is to be proficient in English. The GMAT requires excellent reading comprehension skills, mastery of Standard English grammar, rich vocabulary.
The Verbal section has several types of questions: - Reading Comprehension - Critical Reasoning - Sentence Correction
Although the GMAT is a test for business schools, you will have texts from different subject areas. This replicates real-life situations when managers have to use information from areas in which they are not experts.