Start using gmatclub as a resource:
https://gmatclub.com/forum/gmat-study-plan-217827.html
https://gmatclub.com/forum/how-to-improve-your-quant-from-q44-to-q50-141670.html
Look up the problems you get wrong on gmatclub and search for the pro’s answers. They’re very intuitive and help a ton since the questions are all very similar.