as I have always seen that people score around 30 - 50 more in real GMAT than they score in MGMAT.
That's not actually true. People most often score within a 50 point range in either direction on the real GMAT - up AND down. But people who do better are more likely to tell others, so that may be why you read about that more on the forums.
Your quant score was about the same but your verbal score really dropped. How was your stamina? How was your timing? Did you have a string of questions wrong towards the end or did you run out of time?
If we consider first 10 questions, then I did 7/10 correct in quanta and 8/10 correct in verbal.
It is a complete myth that the earlier questions are worth more. You can do what you did here and still get a lower score, as you saw. Your performance throughout the entire section matters. If you, for example, spend extra time at the beginning in order to get those extra questions right, and then have to rush at the end, your score will most likely be lower than if you had just worked your way steadily through the test, letting go when the questions were too hard or would take too long - sometimes MUCH lower.
The biggest negative on this test is to have a string of questions wrong in a row. The penalty increases for each question wrong in a row. In addition, the penalty is greater for a lower-ranked question. So if you are low on the time at the end and have to start rushing or even guessing, you increase the chances that you both get lower-ranked questions wrong and have multiple wrong in a row. That kills your score.
SC was clearly a problem on this last test - but why? Were you really struggling with the rules? Or were you having some timing issues and having to guess or rush - and that brought your performance down? Figure out why and then you know what to do about it.
If you're struggling with the actual grammar, then you need to review whatever book or books you've been using to learn the grammar (that is, something similar to our Sentence Correction Strategy Guide - something that actually teaches you what you need to know for this test). If you already have something, return to that. If not, identify something (it should be specific to the GMAT, so from a GMAT test-prep company). You may want to go to a bookstore so you can browse through the different options.
If part of your problem is the timing, though, then you need to fix that. It will help, to start, that you now know the "early questions are worth more" myth is actually a myth and you shouldn't pay attention to it. The key is steady performance over the entire section, and that will sometimes require letting "too hard" problems go.