Shld I leave the remain qns not answer or randomly check !

Perhaps you're already doing this, but try to save time throughout the test by quickly making educated guesses on questions that you don't understand (and would probably miss anyway)... and that way, you'll hopefully have enough time left to finish strongly, instead of scrambling at the end.

If you do run out of time, it's probably best to guess randomly on any questions that are left at the end, rather than leave them blank. The penalty for leaving the questions blank isn't necessarily all that severe, though--there was a great post on the official GMAT blog that addressed this issue. Check it out if you get a chance, the article is pretty interesting.

Good luck!