How to improve?

From my experience, Your quant. could be improved in a short time if you worked on it much faster than the verbal.

For the quant,
if you gonna do it without a course, GMATclub has all you need. you should study are related theories and train on much harder questions than the official guide.https://gmatclub.com/forum/all-you-need-for-quant-140445.html#p1130136
however, Always answer questions from known sources only (as Manhattan, veritas and others known tutoring websites)
if you need a fast improvement in a short time, many users recommend "Math Revolution Short-Cut 51" because it is only a one month course but intensive.

For the verbal,
I recommend Manhattan for verbal in general, and e-gmat for SC only.
But don't expect much improvement in verbal

My advice is to focus on quant to nail it till you reach at least Q50. At this point, reaching V34 would be more than enough in verbal to achieve your target.