desertEagle - Since you're a non-native speaker of the language, it is important that you look at courses that are designed keeping a non-native student in mind. It is important that you approach Verbal in a step-by-step fashion developing one skill at a time.
On GMAT Verbal, you are tested on 3 different skills - Comprehension (your ability to comprehend complex sentences with 100% clarity), Analytical Reasoning (your ability to connect multiple pieces of information together and understanding what can be inferred and what can't be inferred) and Identifying the main Intent (your ability to focus on the Main Idea of the text).
Since GMAT RC tests you on all 3 skills and SC tests you solely on Comprehension skill, it is recommended that you start with the SC section first. In fact, at
GMATWhiz, we have developed the entire course curriculum keeping this Skill based learning model in mind. You can check out the free trial of our course here
https://learn.gmatwhiz.com/?page=signupIf you would like to connect with our team and understand how we can help you improve your scores, please feel free to reach out to us using this link:
https://www.calendly.com/gmatwhiz