It's a GL, not a RL 
It HAS to shoot with arc trajectory because of ballistic law. You can knee and this will increase shooting range for a few tiles.
Even so, the ballistic arc shouldn't be
that aggressive, surely. I probably could've
thrown grenades more effectively than using the 46mm launcher, which is kind of daft, because it implies that if you aimed the thing horizontally and fired, the round wouldn't go more than a few feet/meters before hitting dirt.
Hey, I'm just starting out and am still have to use cars and vans for transportation, and my weapons are handguns, shotguns, and a couple Calico SMG's I took from cultists. How do I fight sectoids? It seems like they take my guys out in one shot as soon as I start. If I shoot them, it doesn't put them down and their reaction fire instantly burns through any cover and kills in 1 hit. If I try to move from the starting position, their reaction fire hits my guy and kills them in 1 hit.
In regular Xcom, you start with several guys and longer range weaponry. How am I supposed to fight them with 2 shotguns or 2 pistols? Do I just have to avoid them until I get explosives?
'Just starting out', yet you're encountering aliens at... what month/year exactly? Sectoids have a psi-shield that absorbs a limited amount of damage per turn, so you need to focus them down with accurate fire from carbines or assault rifles at the very least.
Focus on the cults, as they're your main means of getting access to better equipment early on.
