Sneak Attacks for Rogues

You can get a sneak attack under two different scenarios:
1. When you have advantage on your roll. Then you get to roll twice for the advantage and your get to add your sneak attack
2. You do not have advantage but another enemy of your enemy is threatening the enemy you are attacking. Then you get the sneak attack (extra d6 damage) but not the advantage roll to hit.
You can hide, attack and re-hide using your bonus action. But of course the scenario must make sense. If you are just behind a barrel and you come out and shoot – just popping back down behind the same barrel does not work. But if you are in a forest behind a bush you can shoot from behind the bush, through the bush, or you can shoot and move to anther bush and hide again.
A creature can Hide in combat. The creature must be at least heavily obscured (exception is Wood Elf allows for light natural obscurement and lightfoot halfing is great at stealth and can hide even when they were just spotted and can attempt to hide even behind another creature that is at least one size larger than the halfling) and must pass a Stealth check vs the Passive Perception of the enemies. If the creature leaves the cover that allows to Stealth they are auto-detected, otherwise they are not detected until they reveal themselves. Like after firing a ranged weapon from cover.
Keep in mind that a creature can be hidden from some and not all.
Keep in mind light obscurement gives DisAdvantage on Perception checks (so -5 to Passive Perception) that rely on sight.
Keep in mind heavy obscurement creates the blinded condition which is auto-failure for Perception checks that rely on sight.