manneken,
It sounds like you're going through that initial period of shock after your first practice test. From experience, students who are in the 500-range on first take can improve to the low 600s with moderate practice and upper 600s with heavy practice. And those who score upper 600s into low 700s go beyond heavy practice and use smart practice.
Practice might make perfect for somethings in life -- but for the GMAT, it's a test about reasoning. The only way to score beyond your upper range is to change how you think. That's why I highly recommend students to browse some of the free materials at GMAT Pill - there's
sample SC and
RC videos which show you how an expert thinks. That's an important indicator for comprehension -- as you said, you're stuck on understanding what the question stem or passage is saying. That costs you time. And ultimately costs you on the exam. You want to go in knowing how to tackle your "reading" skills -- I'm not just talking about reading comprehension passages. I'm talking about question stems in sentence correction or critical reasoning -- which gives you a whole paragraph of content to digest.
As in the real world, you're going to need to parse through paragraphs of information and decipher. This test helps gauge that ability. So, to your question, is it possible to go from 500 to 700? Yes, but not just through lots of practice. You need smart strategies as well.