Spend time strengthening your foundation. Really review answer choices. When reviewing, highlight grammatical concepts that confuse you and research them on the web. Then, apply the learnings to similar GMAT problems. Reviewing your work is a crucial part of learning.
I noticed in your question used the verb 'do scored', the sentence should read:
"My quantitative scores are fine, but I scored poorly on my....."
If my response helps, please add throw me a kudos.
Jim Kernan is the Director of GMAT Operations at Stratus Prep and author of GMAT Materials for GMAT Prepster.