Level is called "Maelstrom".
Up until this point the game is very easy and simple, but this level can and will cause a lot of frustration. The most frustrating thing - there are 3 sub-parts to the mission, but there are NO checkpoints! At all. Therefore, play on Easy to minimize your grief.
Your task is to escape with the German scientist in a tank. When choosing your soldier, choose Bull (Sniper class).
The trick is not to even enter the tank until you clear all danger from the section. In the first section there is about 15 soldiers, three panzerschreck soldiers on the balconies, and one tank. Each soldier can be killed with one bullet, doesn't even have to be a headshot. Use hand-grenades for groups of enemies, there's plenty of them laying around. Tank takes two panzerschreck rockets. Panzerschreck can first be picked up in the doorway of the first house on the right, and there will be plenty of ammo for it left around by dead Germans. Once you destroy the tank and make sure all foot soldiers are dead, go back and drive the tank to the next section, immediately turn left, park it and get out.
There will be about 6-7 enemies to kill right then, but since you're on foot, they will not bother to shoot and damage the tank. There are more foot soldiers and panzerschreck shooters on balconies, as well as another tank. Be somewhat careful, but you should be ok. Once everybody is cleared, and all the ammo picked up, you can advance to the final section. Tank should be at full health, or almost full.
This next section is the most dangerous one. As soon as you pass through the archway and enter the battlefield, there will be tanks and panzerschrecks aiming at you. Turn immediately to the left, and try to park the tank as close to the back wall as possible. Get out and beware of foot soldiers and a nearby tank and a panzerschreck on the hill. Your tank will get damaged here, but as long as you keep away from it, it will not get targeted any more.
I just lobbed several grenades at the soldiers, and then tried to use cover as much as possible until I took out the tank (hiding behind a central courtyard/graveyard), and the panzerschreck on the hill. There is a rope attached to that hill you can climb. Use it to scout the area, and also to retreat if the things get too tough. There are two more tanks to destroy, which you might be able to hit from there, along with several soldiers. I would just do quick guerilla runs, take one shot then retreat. Once that's done, you only have one more enemy, a panzerschreck on a high tower on the left of your goal. Take him out, carefully check around for any laggards, then go back to the tank, blast the gate blocking your goal, cutscene, achievement unlocked.
It might seem simpler than it is, but this level frustrated me a lot, as I would get killed by a random laggard panzerschreck, or someone would just destroy my tank for no apparent reason.
If you try to advance to the next section on foot, there will be a message that the tank is destroyed. Also, if you try to park the tank in the doorway prior to the last section, as soon as you run in, the doorway collapses and destroys your tank.
You will on occasion have a couple of allied soldiers aiding you, but do not rely on them, they'll die quickly and do not help much.
Do not rush, take your time, it's better to spend two extra minutes walking around checking for stragglers, than having to redo the entire level.
I tried doing it with other two soldiers, and for the first two sections it makes no real difference, but being able to climb that rope and hide on the hill at the end really makes things much easier.