Not only you need to cut off, but you also need to learn not to get angry or disrupted for the next questions.
Picture this: you're standing on a tennis court. The other person hits a good shot. You think you should be able to get it, but you miss it, or you hit it into the net.
Now, you turn to your friend on the other side of the net, glare at her, and say in an angry voice, "I should have had that! You shouldn't have won that point!!"
:) You probably wouldn't keep your friend for very long.
And, really, you're not
that upset about missing it. It's just one point. And you know you're going to lose a bunch of points. After all, how boring would it be to play a tennis match against someone and win EVERY SINGLE POINT! You'd start to feel bad for the other person.
So turn this into a tennis match. Not only aren't you that upset when you lose one point, you outright EXPECT to lose many points over the course of the match. That's okay - you just want to win more than your opponent. :)
But towards the end and when reaching the 700-800 level, I struggle with concentration and also with time.
You can fix this if you learn to cut yourself off effectively on the too-hard problems. Think about it: your brain is getting tired towards the end of the section. It would be less tired if you stopped trying to answer the absolute hardest questions and instead cut yourself off faster. You would then have the energy you need to finish off that section (and then take a short break).
You're not just saving time when you cut yourself off. You're also saving mental energy. There are times that a question will pop up and I'll think "No, thanks - not interested"
even when I have the time! When the question is going to take too much brain energy, I consider NOT doing the stupid problem in the first place!
Back to our tennis analogy: you can run flat out for every single ball. But, at some point, you're going to run out of energy. You need to make sure you have energy till the end of the match, so it's to your advantage to realize that you're not going to get to a certain ball - don't waste energy running for it.
So, yes, to answer both of your questions about cutting yourself off on some questions. If something's too complicated or going to take too much time, forget it. Figure out how to guess, then move on.
As far as we can tell, the algorithm works the same way on both quant and verbal - there isn't a significant difference in the way that getting a question wrong will affect your score. I'm guessing you might be reacting to different question difficulty levels on RC. On RC, though, the 3 or 4 questions are chosen for you at the start of the passage - they are not adaptive within the passage. Further, some question types (such as main idea) are just inherently easier than others, so you may get a question wrong and then see a much easier Main Idea... but that question was already chosen for you before you answered the first question!
Here are some resources for you on RC and CR:
https://www.manhattangmat.com/blog/inde ... reasoning/https://www.manhattangmat.com/blog/inde ... rehension/Careless mistakes:
http://www.manhattangmat.com/blog/index ... -the-gmat/Speed drills, solving 20-30 questions in max. 30 minutes.
This is fine as long as you know that your goal is NOT to get everything right in that time. It's about how to make the best decisions about how to spend your time and mental energy, which sometimes does mean letting something go.
Finally, re: your question about doing OG questions (vs. ours or questions from another non-official source), it's not a good idea to be doing only non-official questions for long periods of time. We (the test prep companies) all do our absolute best to mimic the real test questions, but we are still not the real test writers. So do some of our questions, yes, but also do OG questions throughout your studies.