Hi there,
I do not offer online courses, but I tutor many non-native speakers of GMAT Verbal. Regardless of what tutor you choose, there's definitely some set tips I'd recommend for ANY non-native speaker:
Build your grammar skills first. You can ignore most of the challenging vocabulary on sentence corrections as long as you identify what part of speech each word is, and how it functions within the sentence. To do this, you'll need to spend some time with a solid English grammar review book. I recommend pairing a heavy-duty review book, like the Oxford Guide or those published by McGraw-Hill or Longman, with a "fun" book like Writer's Express or English Grammar for Dummies. Start identifying the subject and the verb of every sentence correction, as well as any dependent clauses. Strategy alone won't get you the Verbal score you want. Start your Verbal studying with grammar.
RC practice becomes EXTRA important, but since you have 3-4 months, you can really build it from the ground up. Here's where I'd suggest you look for challenging text to practice RC note-taking and interpretation:
https://gmatrockstar.com/2013/11/08/wher ... -speakers/
Good luck!
