Im having trouble with "Behind Enemy Lines" any tips?
What I'd advise is to take your time. You're not in a hurry. First, make sure to get the best cover you can. A good tip is to always put fire on hold. This way, you can fully approach without firing. And when you take it off, you can see if you're able to hit them. If you're not, move closer. Taking off firing at will will also help when dealing with mortars, anti-tank, MGs. They'll never attack.
For example, to kill the first officer, I move Ania slightly to the right (next to a truck, I believe) and I move my snipers one by one. I put one front and the other slightly behind. The point is to cover a potential retreat and incoming enemies. I usually shot 1, maybe 2 times then I'm retreating. If you can spread your sniper over an area, do it, but be careful. It must be wide enough that a unit can't fire at all at once but close enough so they can all shoot the unit.
Usually, Ania is good at taking snipers, mortars teams. She's a good bait to lure your enemies in an ambush by how resistant she is (she can take a mortar shell and only lose half her life).
When you'll be in need to protect Ania, I'd suggest to eliminate every squad around the informant and start planting demolitions charges on the different pathways. This way, once you've reached the mission, you can remain in cover (use good cover, so green). Call a squad. More if necessary. Then, if you've survived this, the rest's easy. You make your way toward the camp, stay in cover, eliminate everyone, liberate the prisoner, take an anti-infantery and anti-tanks partisans and then you make your way back. It's easier, imo, if you go toward your first starting point. You'll avoid most of the troops (till the end where there might be 2/3 units to easily deal with and probably a quick skirmish in the middle).
hope this helped.