Was leaning over on my phone for a few minutes when i stood up 3/4ths of my vision blacked out. was this just orthostatic hypotension and is it benign?

You are correct: This is orthostatic hypotension, which in a young person usually indicates some degree of dehydration. This is much more likely if you are in a hot environment. Be sure to drink enough water so that when voiding, the urine looks like water to be sure that you are not dehydrated at all. Changing posture a little more slowly will also prevent this by giving more time for adjustment of the bp.